Item 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA

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Item 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA


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REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Shareowners and the Board of Directors of Alliant Energy Corporation:

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Alliant Energy Corporation and subsidiaries (the “Company”) as of December 31, 2023 and 2022, the related consolidated statements of income, equity, and cash flows, for each of the three years in the period ended December 31, 2023, and the related notes and the schedules listed in the Index at Item 15 (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company’s internal control over financial reporting as of December 31, 2023, based on criteria established in Internal Control - Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 16, 2024, expressed an unqualified opinion on the Company’s internal control over financial reporting.

Basis for Opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the PCAOB and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current-period audit of the financial statements that was communicated or required to be communicated to the audit committee and that (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Regulatory Accounting - Impact of rate regulation on the financial statements - Refer to Notes 1, 2, and 3 to the financial statements

Critical Audit Matter Description

Alliant Energy Corporation, through its wholly-owned subsidiaries Interstate Power and Light Company and Wisconsin Power and Light Company, is subject to rate regulation by regulatory agencies. Management has determined it meets the requirements under accounting principles generally accepted in the United States of America to prepare its financial statements applying the Regulated Operations Topic 980 of the Financial Accounting Standards Board’s Accounting Standards Codification.

The Company’s rates are subject to regulatory rate-setting processes and periodic earnings oversight. The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital. Regulatory assets represent incurred costs that have been deferred and are probable of recovery in future customer rates. Regulatory liabilities represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred. The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies. A change in these rulings may result in a material impact on results of operations and the amount of certain assets and liabilities in the financial statements. Future regulatory rulings may impact the carrying value and accounting treatment of certain regulatory assets and regulatory liabilities.


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We identified the impact of rate regulation as a critical audit matter due to the significant judgments made by management to support its assertions about certain impacted account balances and disclosures and the high degree of subjectivity involved in assessing the impact of relevant future regulatory orders on the financial statements. Management judgments include assessing the likelihood of the recovery of incurred costs and refund of obligations to customers in future rates. Given that management’s accounting judgments are based on assumptions about the outcome of future decisions by the regulatory agencies, auditing these judgments required specialized knowledge of accounting for rate regulation and the rate-setting process due to its inherent complexities.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the regulatory filings by management and the uncertainty of future decisions by the regulatory agencies included the following, among others:

We tested the effectiveness of management’s controls over the evaluation of certain regulatory assets and regulatory liabilities, including the monitoring and evaluation of regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates.
We inspected and evaluated the Company’s analysis supporting the probability of recovery for certain regulatory assets or refund to customers or future reduction in customer rates for regulatory liabilities not yet addressed in a regulatory order to assess management’s assertions.
We inquired of management regarding current events impacting the Company and inspected minutes of the board of directors and other committees of the Company and evaluated whether matters were identified that may have an impact on certain recorded regulatory assets and liabilities.
We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company. We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities.
We inspected minutes of the board of directors and other committees of the Company, regulatory orders and other filings with the regulatory agencies to identify evidence that may contradict management’s assertion regarding probability of abandonment or that may have an impact on the recorded balances.
We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded.

/s/ DELOITTE & TOUCHE LLP

Milwaukee, Wisconsin

February 16, 2024

We have served as the Company’s auditor since 2002.


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Table of C o ntents

ALLIANT ENERGY CORPORATION

CONSOLIDATED STATEMENTS OF INCOME


	Year Ended December 31,
	2023	2022	2021
	(in millions, except per share amounts)
Revenues:
Electric utility	$3,345	$3,421	$3,081
Gas utility	540	642	456
Other utility	52	49	49
Non-utility	90	93	83
Total revenues	4,027	4,205	3,669
Operating expenses:
Electric production fuel and purchased power	736	830	642
Electric transmission service	583	573	537
Cost of gas sold	299	389	258
Other operation and maintenance	675	704	676
Depreciation and amortization	676	671	657
Taxes other than income taxes	115	110	104
Total operating expenses	3,084	3,277	2,874
Operating income	943	928	795
Other (income) and deductions:
Interest expense	394	325	277
Equity income from unconsolidated investments, net	(61)	(51)	(62)
Allowance for funds used during construction	(100)	(60)	(25)
Other	3	6	5
Total other (income) and deductions	236	220	195
Income before income taxes	707	708	600
Income tax expense (benefit)	4	22	(74)


Net income	703	686	674
Preferred dividend requirements of Interstate Power and Light Company	—	—	15
Net income attributable to Alliant Energy common shareowners	$703	$686	$659
Weighted average number of common shares outstanding:
Basic	253.0	250.9	250.2
Diluted	253.3	251.2	250.7




Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic and diluted)	$2.78	$2.73	$2.63

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

CONSOLIDATED BALANCE SHEETS


	December 31,
	2023	2022
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$62	$20
Accounts receivable, less allowance for expected credit losses	475	516
Production fuel, at weighted average cost	62	53
Gas stored underground, at weighted average cost	79	132
Materials and supplies, at weighted average cost	202	140
Regulatory assets	232	166

Other	160	223
Total current assets	1,272	1,250
Property, plant and equipment, net	17,157	16,247
Investments:
ATC Holdings	386	358
Other	216	201
Total investments	602	559
Other assets:
Regulatory assets	2,029	1,880
Deferred charges and other	177	227
Total other assets	2,206	2,107
Total assets	$21,237	$20,163


LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt	$809	$408
Commercial paper	475	642

Accounts payable	611	756


Regulatory liabilities	107	206
Other	302	351
Total current liabilities	2,304	2,363
Long-term debt, net (excluding current portion)	8,225	7,668
Other liabilities:
Deferred tax liabilities	2,042	1,943
Regulatory liabilities	1,023	1,118
Pension and other benefit obligations	249	277
Other	617	518
Total other liabilities	3,931	3,856
Commitments and contingencies (Note 17)
Equity:
Alliant Energy Corporation common equity:
Common stock - $0.01 par value - 480,000,000 shares authorized; 256,096,848 and 251,134,966 shares outstanding	3	3
Additional paid-in capital	3,030	2,777
Retained earnings	3,756	3,509
Accumulated other comprehensive income	1	—
Shares in deferred compensation trust - 379,006 and 402,134 shares at a weighted average cost of $34.48 and $32.63 per share	(13)	(13)
Total Alliant Energy Corporation common equity	6,777	6,276


Total liabilities and equity	$21,237	$20,163

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

CONSOLIDATED STATEMENTS OF CASH FLOWS


	Year Ended December 31,
	2023	2022	2021
	(in millions)
Cash flows from operating activities:
Net income	$703	$686	$674
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	676	671	657

Deferred tax expense (benefit) and tax credits	14	13	(78)


Equity component of allowance for funds used during construction	(74)	(44)	(18)
Other	35	27	35
Other changes in assets and liabilities:
Accounts receivable	(414)	(672)	(530)
Materials and supplies	(62)	(27)	(13)
Regulatory assets	24	(108)	51
Derivative assets	149	(61)	(142)
Accounts payable	(122)	78	37
Regulatory liabilities	(149)	22	(66)
Derivative liabilities	19	70	(17)
Deferred income taxes (a)	84	4	193
Pension and other benefit obligations	(28)	(97)	(137)

Other	12	(76)	(64)
Net cash flows from operating activities	867	486	582
Cash flows used for investing activities:
Construction and acquisition expenditures:
Utility business	(1,731)	(1,392)	(1,070)
Other	(123)	(92)	(99)
Cash receipts on sold receivables	453	598	502
Proceeds from sales of partial ownership interests in West Riverside	120	—	—
Other	(120)	(47)	(61)
Net cash flows used for investing activities	(1,401)	(933)	(728)
Cash flows from financing activities:
Common stock dividends	(456)	(428)	(403)
Proceeds from issuance of common stock, net	246	25	28
Payments to redeem cumulative preferred stock of IPL	—	—	(200)
Proceeds from issuance of long-term debt	1,455	1,338	600
Payments to retire long-term debt	(508)	(633)	(8)
Net change in commercial paper	(167)	127	126


Other	3	2	(13)
Net cash flows from financing activities	573	431	130
Net increase (decrease) in cash, cash equivalents and restricted cash	39	(16)	(16)
Cash, cash equivalents and restricted cash at beginning of period	24	40	56
Cash, cash equivalents and restricted cash at end of period	$63	$24	$40
Supplemental cash flows information:
Cash (paid) refunded during the period for:
Interest	($378)	($311)	($272)
Income taxes, net (a)	$88	($6)	($3)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$364	$382	$141
Beneficial interest obtained in exchange for securitized accounts receivable	$216	$185	$214

(a) 2023 includes $98 million of proceeds from renewable tax credits transferred to other corporate taxpayers

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

CONSOLIDATED STATEMENTS OF EQUITY


	Total Alliant Energy Common Equity
				Accumulated	Shares in	Cumulative
		Additional		Other	Deferred	Preferred
	Common	Paid-In	Retained	Comprehensive	Compensation	Stock	Total
	Stock	Capital	Earnings	Income (Loss)	Trust	of IPL	Equity
	(in millions)
2021:
Beginning balance	$2	$2,704	$2,994	($1)	($11)	$200	$5,888
Net income attributable to Alliant Energy common shareowners			659				659
Common stock dividends ($1.61 per share)			(403)				(403)
Shareowner Direct Plan issuances	1	27					28
Equity-based compensation plans and other		18			(1)		17
Redemption of IPL’s cumulative preferred stock						(200)	(200)

Other comprehensive income, net of tax				1			1
Ending balance	3	2,749	3,250	—	(12)	—	5,990
2022:
Net income attributable to Alliant Energy common shareowners			686				686
Common stock dividends ($1.71 per share)			(428)				(428)
Shareowner Direct Plan issuances		25					25
Equity-based compensation plans and other		3	1		(1)		3





Ending balance	3	2,777	3,509	—	(13)	—	6,276
2023:
Net income attributable to Alliant Energy common shareowners			703				703
Common stock dividends ($1.81 per share)			(456)				(456)
At-the-market offering program, net and Shareowner Direct Plan issuances		246					246
Equity-based compensation plans and other		7					7



Other comprehensive income, net of tax				1			1
Ending balance	$3	$3,030	$3,756	$1	($13)	$—	$6,777

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Shareowner and the Board of Directors of Interstate Power and Light Company:

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Interstate Power and Light Company and subsidiaries (the “Company”) as of December 31, 2023 and 2022, the related consolidated statements of income, equity, and cash flows, for each of the three years in the period ended December 31, 2023, and the related notes and the schedule listed in the Index at Item 15 (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

Regulatory Accounting - Impact of rate regulation on the financial statements - Refer to Notes 1, 2, and 3 to the financial statements

Critical Audit Matter Description

Interstate Power and Light Company is subject to rate regulation by regulatory agencies. Management has determined it meets the requirements under accounting principles generally accepted in the United States of America to prepare its financial statements applying the Regulated Operations Topic 980 of the Financial Accounting Standards Board’s Accounting Standards Codification.


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How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the regulatory filings by management and the uncertainty of future decisions by the regulatory agencies included the following, among others:

We tested the effectiveness of management’s controls over the evaluation of certain regulatory assets and regulatory liabilities, including the monitoring and evaluation of regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates.
We inspected and evaluated the Company’s analysis supporting the probability of recovery for certain regulatory assets or refund to customers or future reduction in customer rates for regulatory liabilities not yet addressed in a regulatory order to assess management’s assertions.
We inquired of management regarding current events impacting the Company and inspected minutes of the board of directors and other committees of the Company and evaluated whether matters were identified that may have an impact on certain recorded regulatory assets and liabilities.
We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company. We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities.
We inspected minutes of the board of directors and other committees of the Company, regulatory orders and other filings with the regulatory agencies to identify evidence that may contradict management’s assertion regarding probability of abandonment or that may have an impact on the recorded balances.
We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded.

/s/ DELOITTE & TOUCHE LLP

Milwaukee, Wisconsin

February 16, 2024

We have served as the Company’s auditor since 2002.


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INTERSTATE POWER AND LIGHT COMPANY

CONSOLIDATED STATEMENTS OF INCOME


	Year Ended December 31,
	2023	2022	2021
	(in millions)
Revenues:
Electric utility	$1,761	$1,859	$1,752
Gas utility	300	351	265
Steam and other	49	46	46
Total revenues	2,110	2,256	2,063
Operating expenses:
Electric production fuel and purchased power	282	383	295
Electric transmission service	420	407	367
Cost of gas sold	166	206	149
Other operation and maintenance	353	369	362
Depreciation and amortization	388	381	375
Taxes other than income taxes	57	57	55
Total operating expenses	1,666	1,803	1,603
Operating income	444	453	460
Other (income) and deductions:
Interest expense	155	148	139
Allowance for funds used during construction	(21)	(11)	(9)
Other	2	6	1
Total other (income) and deductions	136	143	131
Income before income taxes	308	310	329
Income tax benefit	(58)	(50)	(36)
Net income	366	360	365
Preferred dividend requirements	—	—	15
Net income available for common stock	$366	$360	$350

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented.

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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INTERSTATE POWER AND LIGHT COMPANY

CONSOLIDATED BALANCE SHEETS


	December 31,
	2023	2022
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$53	$15
Accounts receivable, less allowance for expected credit losses	242	259

Production fuel, at weighted average cost	27	23
Gas stored underground, at weighted average cost	35	60
Materials and supplies, at weighted average cost	122	83
Regulatory assets	93	85
Other	51	93
Total current assets	623	618
Property, plant and equipment, net	8,298	8,046
Other assets:
Regulatory assets	1,484	1,301
Deferred charges and other	84	110
Total other assets	1,568	1,411
Total assets	$10,489	$10,075


LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt	$500	$—

Accounts payable	262	239

Accrued taxes	50	52
Accrued interest	40	35
Regulatory liabilities	72	114
Other	101	141
Total current liabilities	1,025	581
Long-term debt, net (excluding current portion)	3,445	3,646
Other liabilities:
Deferred tax liabilities	1,091	1,047
Regulatory liabilities	572	640
Pension and other benefit obligations	51	62
Other	331	291
Total other liabilities	2,045	2,040
Commitments and contingencies (Note 17)
Equity:
Interstate Power and Light Company common equity:
Common stock - $2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding	33	33
Additional paid-in capital	2,887	2,807
Retained earnings	1,054	968
Total Interstate Power and Light Company common equity	3,974	3,808


Total liabilities and equity	$10,489	$10,075

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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INTERSTATE POWER AND LIGHT COMPANY

CONSOLIDATED STATEMENTS OF CASH FLOWS


	Year Ended December 31,
	2023	2022	2021
	(in millions)
Cash flows from operating activities:
Net income	$366	$360	$365
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	388	381	375


Other	(2)	(21)	(10)
Other changes in assets and liabilities:
Accounts receivable	(437)	(611)	(539)
Materials and supplies	(39)	(13)	(7)
Regulatory assets	58	56	30
Derivative assets	84	(54)	(55)

Accounts payable	(68)	65	15
Regulatory liabilities	(92)	53	1
Derivative liabilities	(16)	42	(8)
Deferred income taxes (a)	36	(24)	62
Pension and other benefit obligations	(11)	(65)	(59)

Other	(6)	(86)	(17)
Net cash flows from operating activities	261	83	153
Cash flows from (used for) investing activities:
Construction and acquisition expenditures	(712)	(372)	(384)
Cash receipts on sold receivables	453	598	502
Other	(67)	(11)	(27)
Net cash flows from (used for) investing activities	(326)	215	91
Cash flows from (used for) financing activities:
Common stock dividends	(280)	(321)	(400)
Capital contributions from parent	80	—	50
Payments to redeem cumulative preferred stock	—	—	(200)
Proceeds from issuance of long-term debt	296	—	300


Other	7	4	(10)
Net cash flows from (used for) financing activities	103	(317)	(260)
Net increase (decrease) in cash, cash equivalents and restricted cash	38	(19)	(16)
Cash, cash equivalents and restricted cash at beginning of period	15	34	50
Cash, cash equivalents and restricted cash at end of period	$53	$15	$34
Supplemental cash flows information:
Cash (paid) refunded during the period for:
Interest	($150)	($148)	($138)
Income taxes, net (a)	$117	$36	$47
Significant non-cash investing and financing activities:
Accrued capital expenditures	$140	$56	$57
Beneficial interest obtained in exchange for securitized accounts receivable	$216	$185	$214

(a) 2023 includes $76 million of proceeds from renewable tax credits transferred to other corporate taxpayers

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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INTERSTATE POWER AND LIGHT COMPANY

CONSOLIDATED STATEMENTS OF EQUITY


	Total IPL Common Equity
		Additional		Cumulative
	Common	Paid-In	Retained	Preferred	Total
	Stock	Capital	Earnings	Stock	Equity
	(in millions)
2021:
Beginning balance	$33	$2,752	$979	$200	$3,964
Net income available for common stock			350		350
Common stock dividends			(400)		(400)
Capital contributions from parent		50			50
Redemption of cumulative preferred stock				(200)	(200)
Other		5			5
Ending balance	33	2,807	929	—	3,769
2022:
Net income available for common stock			360		360
Common stock dividends			(321)		(321)



Ending balance	33	2,807	968	—	3,808
2023:
Net income available for common stock			366		366
Common stock dividends			(280)		(280)
Capital contributions from parent		80			80

Ending balance	$33	$2,887	$1,054	$—	$3,974

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Shareowner and the Board of Directors of Wisconsin Power and Light Company:

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Wisconsin Power and Light Company and subsidiaries (the “Company”) as of December 31, 2023 and 2022, the related consolidated statements of income, equity, and cash flows, for each of the three years in the period ended December 31, 2023, and the related notes and the schedule listed in the Index at Item 15 (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2023 and 2022, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2023, in conformity with accounting principles generally accepted in the United States of America.

Basis for Opinion

These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion.

Critical Audit Matter

Regulatory Accounting - Impact of rate regulation on the financial statements - Refer to Notes 1, 2, and 3 to the financial statements

Critical Audit Matter Description

Wisconsin Power and Light Company is subject to rate regulation by regulatory agencies. Management has determined it meets the requirements under accounting principles generally accepted in the United States of America to prepare its financial statements applying the Regulated Operations Topic 980 of the Financial Accounting Standards Board’s Accounting Standards Codification.


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How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to the regulatory filings by management and the uncertainty of future decisions by the regulatory agencies included the following, among others:

We tested the effectiveness of management’s controls over the evaluation of certain regulatory assets and regulatory liabilities, including the monitoring and evaluation of regulatory developments that may affect the likelihood of recovering costs in future rates or of a future reduction in rates.
We inspected and evaluated the Company’s analysis supporting the probability of recovery for certain regulatory assets or refund to customers or future reduction in customer rates for regulatory liabilities not yet addressed in a regulatory order to assess management’s assertions.
We inquired of management regarding current events impacting the Company and inspected minutes of the board of directors and other committees of the Company and evaluated whether matters were identified that may have an impact on certain recorded regulatory assets and liabilities.
We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company. We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities.
We inspected minutes of the board of directors and other committees of the Company, regulatory orders and other filings with the regulatory agencies to identify evidence that may contradict management’s assertion regarding probability of abandonment or that may have an impact on the recorded balances.
We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded.

/s/ DELOITTE & TOUCHE LLP

Milwaukee, Wisconsin

February 16, 2024

We have served as the Company’s auditor since 2002.


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WISCONSIN POWER AND LIGHT COMPANY

CONSOLIDATED STATEMENTS OF INCOME


	Year Ended December 31,
	2023	2022	2021
	(in millions)
Revenues:
Electric utility	$1,584	$1,562	$1,329
Gas utility	240	291	191
Other	3	3	3
Total revenues	1,827	1,856	1,523
Operating expenses:
Electric production fuel and purchased power	455	447	347
Electric transmission service	163	166	170
Cost of gas sold	134	183	109
Other operation and maintenance	271	278	268
Depreciation and amortization	280	283	276
Taxes other than income taxes	52	47	45
Total operating expenses	1,355	1,404	1,215
Operating income	472	452	308
Other (income) and deductions:
Interest expense	149	121	105

Allowance for funds used during construction	(79)	(49)	(16)
Other	(3)	(1)	2
Total other (income) and deductions	67	71	91
Income before income taxes	405	381	217
Income tax expense (benefit)	60	66	(51)
Net income	$345	$315	$268

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of WPL’s common stock outstanding during the periods presented.

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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WISCONSIN POWER AND LIGHT COMPANY

CONSOLIDATED BALANCE SHEETS


	December 31,
	2023	2022
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$7	$5
Accounts receivable, less allowance for expected credit losses	219	244
Production fuel, at weighted average cost	35	29
Gas stored underground, at weighted average cost	44	73
Materials and supplies, at weighted average cost	77	54
Regulatory assets	139	81
Prepaid gross receipts tax	49	42
Other	43	60
Total current assets	613	588
Property, plant and equipment, net	8,415	7,722
Other assets:
Regulatory assets	545	579
Deferred charges and other	61	98
Total other assets	606	677
Total assets	$9,634	$8,987


LIABILITIES AND EQUITY
Current liabilities:

Commercial paper	$318	$290
Accounts payable	293	456

Accrued interest	40	38
Regulatory liabilities	35	92
Other	89	73
Total current liabilities	775	949
Long-term debt, net	3,070	2,770
Other liabilities:
Deferred tax liabilities	827	789
Regulatory liabilities	451	478

Pension and other benefit obligations	121	140
Other	493	370
Total other liabilities	1,892	1,777
Commitments and contingencies (Note 17)
Equity:
Wisconsin Power and Light Company common equity:
Common stock - $5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding	66	66
Additional paid-in capital	2,478	2,233
Retained earnings	1,353	1,192
Total Wisconsin Power and Light Company common equity	3,897	3,491
Total liabilities and equity	$9,634	$8,987

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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WISCONSIN POWER AND LIGHT COMPANY

CONSOLIDATED STATEMENTS OF CASH FLOWS


	Year Ended December 31,
	2023	2022	2021
	(in millions)
Cash flows from operating activities:
Net income	$345	$315	$268
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	280	283	276

Deferred tax expense (benefit) and tax credits	(13)	4	(79)


Equity component of allowance for funds used during construction	(59)	(36)	(11)
Other	25	21	22
Other changes in assets and liabilities:
Accounts receivable	23	(53)	3
Regulatory assets	(34)	(163)	21
Derivative assets	65	(7)	(87)
Accounts payable	(57)	22	4
Regulatory liabilities	(57)	(31)	(67)
Deferred income taxes (a)	50	32	132
Pension and other benefit obligations	(19)	(19)	(63)
Other	29	(69)	(48)
Net cash flows from operating activities	578	299	371
Cash flows used for investing activities:
Construction and acquisition expenditures	(1,019)	(1,020)	(686)
Proceeds from sales of partial ownership interests in West Riverside	120	—	—
Other	(47)	(13)	(30)
Net cash flows used for investing activities	(946)	(1,033)	(716)
Cash flows from financing activities:
Common stock dividends	(184)	(176)	(168)
Capital contributions from parent	245	530	245
Proceeds from issuance of long-term debt	297	588	300
Payments to retire long-term debt	—	(250)	—
Net change in commercial paper	28	54	(21)


Other	(16)	(9)	(12)
Net cash flows from financing activities	370	737	344
Net increase (decrease) in cash, cash equivalents and restricted cash	2	3	(1)
Cash, cash equivalents and restricted cash at beginning of period	5	2	3
Cash, cash equivalents and restricted cash at end of period	$7	$5	$2
Supplemental cash flows information:
Cash paid during the period for:
Interest	($146)	($111)	($101)
Income taxes, net (a)	($50)	($56)	($38)
Significant non-cash investing and financing activities:
Accrued capital expenditures	$217	$319	$81

(a) 2023 includes $22 million of proceeds from renewable tax credits transferred to other corporate taxpayers

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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WISCONSIN POWER AND LIGHT COMPANY

CONSOLIDATED STATEMENTS OF EQUITY



		Additional
	Common	Paid-In	Retained	Total
	Stock	Capital	Earnings	Equity
	(in millions)
2021:
Beginning balance	$66	$1,459	$953	$2,478
Net income			268	268
Common stock dividends			(168)	(168)
Capital contributions from parent		245		245

Ending balance	66	1,704	1,053	2,823
2022:
Net income			315	315
Common stock dividends			(176)	(176)
Capital contributions from parent		530		530


Other		(1)		(1)
Ending balance	66	2,233	1,192	3,491
2023:
Net income			345	345
Common stock dividends			(184)	(184)
Capital contributions from parent		245		245



Ending balance	$66	$2,478	$1,353	$3,897

Refer to accompanying Combined Notes to Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

INTERSTATE POWER AND LIGHT COMPANY

WISCONSIN POWER AND LIGHT COMPANY

COMBINED NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General -

Description of Business - Alliant Energy’s financial statements include the accounts of Alliant Energy and its consolidated subsidiaries. Alliant Energy is a Midwest U.S. energy holding company, whose primary wholly-owned subsidiaries are IPL, WPL, AEF and Corporate Services.

IPL’s financial statements include the accounts of IPL and its consolidated subsidiaries, including IPL SPE LLC, which is used for IPL’s sales of accounts receivable program. IPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa. IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa, and is engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa.

WPL’s financial statements include the accounts of WPL and its consolidated subsidiaries. WPL is a direct subsidiary of Alliant Energy and is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin. WPL also sells electricity to wholesale customers in Wisconsin.

AEF is comprised of Travero, ATI, corporate venture investments, a non-utility wind farm, the Sheboygan Falls Energy Facility and other non-utility holdings. Travero includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; wind turbine blade recycling services; and a rail-served warehouse in Iowa. ATI, a wholly-owned subsidiary of AEF, holds all of Alliant Energy’s interest in ATC Holdings. Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy. The non-utility wind farm includes a 50% cash equity ownership interest in a 225 MW wind farm located in Oklahoma. The Sheboygan Falls Energy Facility is a 347 MW, simple-cycle, natural gas-fired EGU near Sheboygan Falls, Wisconsin, which is currently leased to WPL through 2039.

Corporate Services is the subsidiary formed to provide administrative services to Alliant Energy and its subsidiaries.

Basis of Presentation - The financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly-owned utility EGUs. Unconsolidated investments that Alliant Energy and WPL do not control are accounted for under the equity method of accounting. Under the equity method of accounting, Alliant Energy and WPL initially record the investment at cost, and adjust the carrying amount of the investment to recognize their respective share of the earnings or losses of the investee. Dividends received from an investee reduce the carrying amount of the equity investment. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method.

All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes. The financial statements are prepared in conformity with GAAP, which give recognition to the rate-making practices of FERC and state commissions having regulatory jurisdiction.

Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

Use of Estimates - The preparation of the financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

NOTE 1(b) Regulatory Assets and Regulatory Liabilities - Alliant Energy, IPL and WPL are subject to regulation by FERC and various state regulatory commissions. As a result, Alliant Energy, IPL and WPL are subject to GAAP provisions for regulated operations, which provide that rate-regulated public utilities record certain costs and credits allowed in the rate-making process in different periods than for non-utility entities. Regulatory assets generally represent incurred costs that have been deferred as such costs are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the related costs have not yet been incurred. Amounts recorded as regulatory assets or regulatory liabilities are generally recognized in the income statements at the time they are reflected in rates.


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NOTE 1(c) Income Taxes - The liability method of accounting is followed for deferred taxes, which requires the establishment of deferred tax assets and liabilities, as appropriate, for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state apportionment. Changes in deferred tax assets and liabilities associated with certain property-related differences at IPL are accounted for differently than other subsidiaries of Alliant Energy due to rate-making practices in Iowa. Rate-making practices in Iowa do not allow the impact of certain deferred tax expenses (benefits) to be included in the determination of retail rates. Based on these rate-making practices, deferred tax expense (benefit) related to these property-related differences at IPL is not recorded in the income statement but instead recorded to regulatory assets or regulatory liabilities until these temporary differences reverse. In Wisconsin, the PSCW allows rate recovery of deferred tax expense on all temporary differences.

The flow-through method of accounting is used for investment tax credits. Certain federal investment tax credits related to utility property, plant and equipment are subject to statutory tax normalization rules limiting how they may be treated in rate-making. As appropriate to reflect the rate-making practices, investment tax credits are deferred and amortized over the book depreciable lives of the related property or other period prescribed by rate regulation.

Alliant Energy files a consolidated federal income tax return and a combined return in Wisconsin, which include Alliant Energy and its subsidiaries. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa.

Alliant Energy allocates consolidated income tax expense to its subsidiaries that are members of the group that file a consolidated or combined income tax return. IPL and WPL use the separate return approach for calculating their income tax provisions and related deferred tax assets and liabilities. IPL and WPL are assumed to file separate tax returns with the federal and state taxing authorities, except that net operating losses (and other current or deferred tax attributes) are characterized as realized (or realizable) by IPL and WPL when those tax attributes are realized (or realizable) by the consolidated tax return group of Alliant Energy (even if IPL and WPL would not otherwise have realized the attributes on a stand-alone basis).

The Inflation Reduction Act of 2022 provides the ability to transfer renewable tax credits to other corporate taxpayers. In 2023, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and battery storage facilities to other corporate taxpayers in exchange for cash. Alliant Energy, IPL and WPL have elected to record transfers of renewable tax credits as part of income taxes. For renewable tax credits subject to future transfer, a valuation allowance is recorded for the difference between the tax value of the credits and the expected sales price. Renewable tax credits and any related valuation allowances are derecognized when control of the tax credits is transferred to other corporate taxpayers. A majority of the differences between actual renewable tax credits and renewable tax credits used to determine rates are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers. The cash received from the transfer of renewable tax credits is recorded in cash flows from operating activities. Refer to Notes 12 and 17(d) for further discussion of the transfer of renewable tax credits to other corporate taxpayers, including related valuation allowances and indemnification requirements, respectively.

NOTE 1(d) Cash, Cash Equivalents and Restricted Cash - Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days. At December 31, 2023, Alliant Energy’s and IPL’s cash and cash equivalents included $45 million of money market fund investments, with a weighted average interest rate of 5%. At December 31, 2023 and 2022, Alliant Energy’s restricted cash related to requirements in Sheboygan Power, LLC’s debt agreement.

NOTE 1(e) Property, Plant and Equipment -

Utility Plant -

General - Utility plant is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, certain administrative costs directly related to construction, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Property, plant and equipment that is probable of being retired early is classified as plant anticipated to be retired early. Generally, ordinary retirements of utility plant and salvage value are netted and charged to accumulated depreciation upon removal from utility plant accounts and no gain or loss is recognized consistent with rate-making principles. However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement.

Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service


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component of rates collected from customers. The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:


	IPL			WPL
	2023	2022	2021	2023	2022	2021
Electric - generation	3.3%	3.4%	3.4%	3.0%	3.4%	3.5%
Electric - distribution	2.8%	2.8%	2.9%	2.7%	2.5%	2.6%
Electric - other	5.6%	5.7%	5.7%	6.3%	6.8%	7.4%
Gas	3.3%	3.3%	3.3%	2.5%	2.4%	2.4%
Other	6.2%	6.1%	6.1%	4.6%	4.9%	5.4%

AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC rates, computed in accordance with the prescribed regulatory formula, were as follows:


	2023	2022	2021
IPL (Wind generation CWIP)	6.9%	6.9%	7.0%
IPL (other CWIP)	7.0%	7.0%	7.2%
WPL (retail jurisdiction)	7.4%	7.0%	7.0%
WPL (wholesale jurisdiction)	7.1%	6.2%	5.6%

In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100% of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50% of applicable CWIP balances and the remaining 50% of applicable CWIP balances earns a return on such balances as part of its rate base. WPL may apply its AFUDC rates to 100% of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs.

Non-utility and Other Property -

General - Non-utility property is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-utility property, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the income statements.

Costs related to software developed or obtained for internal use are capitalized and amortized on a straight-line basis over the estimated useful life of the related software. If software is retired prior to being fully amortized, the remaining book value is recorded as a loss in the income statements.

NOTE 1(f) Revenue Recognition -

Utility - Revenues from Alliant Energy’s utility business are primarily from electric and gas sales to customers. Utility revenues are recognized over time as services are rendered or commodities are delivered to customers, and include billed and unbilled components. The billed component is based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period and represents the fair value of the services provided or commodities delivered. The unbilled component is recorded at the end of each reporting period based on estimated amounts of energy delivered to customers but not yet billed.

IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher or lower than the amounts billed to wholesale customers during such period. Regulatory assets or regulatory liabilities are recorded as the offset for these accrued revenues under formulaic rate-making programs. As of December 31, 2023, the related amounts accrued for IPL and WPL were not material.

IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO. The MISO transactions are grouped together, resulting in a net supply to or net purchase from MISO for each hour of each day. The net supply to MISO is recorded as bulk power sales in “Electric utility revenues” and the net purchase from MISO is recorded in “Electric production fuel and purchased power” in the income statements.

Non-utility - Revenues from Alliant Energy’s non-utility businesses are primarily from its Travero business and are recognized over time as services are rendered to customers.

Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues.


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Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for: (i) contracts with an original expected length of one year or less; and (ii) contracts for which revenue is recognized at the amount to which they have the right to invoice for services performed.

NOTE 1(g) Utility Cost Recovery Mechanisms -

Electric Production Fuel and Purchased Power (Fuel-related Costs) - Fuel-related costs are incurred to generate and purchase electricity to meet the demand of IPL’s and WPL’s electric customers. These fuel-related costs include the cost of fossil fuels (primarily natural gas and coal) used to produce electricity at their EGUs, and electricity purchased from MISO wholesale energy markets and under PPAs. These fuel-related costs are recorded in “Electric production fuel and purchased power” in the income statements.

IPL Retail - The cost recovery mechanisms for IPL’s retail electric customers provide for monthly adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.

WPL Retail - The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. If WPL’s actual fuel-related costs fall outside these fuel monitoring ranges, WPL is authorized to defer the incremental under-/over-collection of fuel-related costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Deferred amounts for fuel-related costs outside the approved fuel monitoring ranges are primarily recognized in “Electric production fuel and purchased power” in Alliant Energy’s and WPL’s income statements. The cumulative effects of these deferred amounts are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until they are reflected in future billings to customers.

IPL and WPL Wholesale - The cost recovery mechanisms for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in fuel-related costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and purchased power” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers.

Electric Capacity - PPAs help meet the electricity demand of IPL’s and WPL’s customers. Certain PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Electric production fuel and purchased power” in the income statements. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to IPL's retail electric customers through changes in base rates determined during periodic rate proceedings, and to IPL and WPL's wholesale electric customers through annual changes in base rates determined by a formula rate structure. Electric capacity revenues are refunded to WPL's retail electric customers through its fuel cost recovery mechanism.

Electric Transmission Service - Costs incurred for the transmission of electricity to meet the demands of IPL’s and WPL’s customers are charged to “Electric transmission service” in the income statements.

IPL Retail - Electric transmission service expense is recovered from IPL’s retail electric customers through a transmission cost rider. This cost recovery mechanism provides for periodic adjustments to electric rates charged to retail electric customers for changes in electric transmission service expense. Changes in the under-/over-collection of these costs are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.

WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual electric transmission service expense incurred and the amount of electric transmission service costs collected from customers as electric revenues is recognized in “Electric transmission service” in Alliant Energy’s and WPL’s income statements. An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers.

IPL and WPL Wholesale - IPL and WPL arrange transmission service for the majority of their respective wholesale electric customers. Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation.


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Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates periodically for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the income statements. The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers.

Energy Efficiency Costs - Costs incurred to fund energy efficiency programs and initiatives that help customers reduce their energy usage are charged to “Other operation and maintenance” in the income statements. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers through energy efficiency and demand response cost recovery factor tariffs, which are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Pursuant to escrow accounting treatment approved by the PSCW, the difference between actual energy efficiency costs incurred by WPL and the amount collected from its retail electric and gas customers is recovered through changes in base rates determined during periodic rate proceedings, and reconciliations eliminate any under-/over-collection of energy efficiency costs from prior periods. Changes in the under-/over-collection of energy efficiency costs for IPL and WPL are recognized in “Other operation and maintenance” in the income statements. The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers.

Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider. Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider. This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits. Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements. The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.

NOTE 1(h) Financial Instruments - Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and interest rates. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the balance sheets. Certain commodity purchase and sales contracts qualified for and were designated under the normal purchase and sale exception, and were accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL have elected to not net the fair value amounts of derivatives subject to a master netting arrangement by counterparty. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments that are executed with the same counterparty under the same master netting arrangement. Refer to Note 2 for discussion of the recognition of regulatory assets and regulatory liabilities related to the unrealized losses and gains on commodity derivative instruments. Refer to Notes 15, 16 and 17(f) for further discussion of derivatives and related credit risk.

NOTE 1(i) Asset Impairments -

Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized.

Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the asset’s fair value.

Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting exceeds fair value and the decline in value is other than temporary, potential impairment is assessed. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value.

NOTE 1(j) Asset Retirement Obligations - The fair value of a legal obligation associated with the retirement of an asset is recorded as a liability when an asset is placed in service, when a legal obligation is subsequently identified or when sufficient information becomes available to determine a reasonable estimate of the fair value of future retirement costs. When an ARO is recorded as a liability, an equivalent amount is added to the asset cost. The fair value of AROs at inception is determined using discounted cash flows analyses. The liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset. Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated


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operations are recorded to regulatory assets on the balance sheets. Revisions in estimated cash flows for IPL’s and WPL’s regulated operations are recorded as an increase or decrease to the ARO liability, with an offset to the asset cost, unless the asset is already retired and then the offset is recorded to regulatory assets or regulatory liabilities on the balance sheets. Upon regulatory approval to recover IPL’s AROs expenditures, its regulatory assets are amortized to depreciation and amortization expenses in Alliant Energy’s and IPL’s income statements over the same time period the ARO expenditures are recovered from IPL’s customers. WPL’s regulatory assets related to AROs are recovered as a component of depreciation rates pursuant to PSCW and FERC orders. Upon settlement of the ARO liability, an entity settles the obligation for its recorded amount or incurs a gain or loss. Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the balance sheets.

NOTE 1(k) Debt Issuance and Retirement Costs - Debt issuance costs and debt premiums or discounts are presented on the balance sheets as a direct adjustment to the carrying amount of the related debt liability, and are deferred and amortized over the expected life of each debt issue, considering maturity dates and, if applicable, redemption rights held by others. Alliant Energy’s non-utility businesses and Corporate Services record to interest expense in the period of retirement any unamortized debt issuance costs and debt premiums or discounts on debt retired early.

NOTE 1(l) Current Expected Credit Losses Estimates - Current expected credit losses are estimated for trade and other receivables and credit exposures on guarantees of the performance by third parties. The current expected credit losses for short-term trade receivables are based on estimates of losses resulting from the inability of customers to make required payments. The methodology used to estimate losses is based on historical write-offs, regional economic conditions, significant events that could impact collectability, such as significant weather related matters and related regulatory actions, and actual and forecasted changes to the accounts receivable aging portfolio and write-offs. The current expected credit losses related to guarantees of the performance by third parties are estimated using both quantitative and qualitative information, which utilizes potential outcomes in a range of possible estimated amounts.

NOTE 1(m) Variable Interest Entities - An entity is considered a VIE if its equity investors do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties, the entity is structured with disproportionate voting rights and substantially all of the entity’s activities are conducted on behalf of the investor with disproportionately fewer voting rights, or its equity investors lack any of the following characteristics: (1) power, through voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb expected losses of the entity; or (3) the right to receive expected benefits of the entity. The primary beneficiary of a VIE is required to consolidate the VIE. The financial statements do not reflect any consolidation of VIEs.

NOTE 1(n) Leases - The determination of whether an arrangement qualifies as a lease occurs at the inception of the arrangement. Arrangements that qualify as leases are classified as either operating or finance. Operating and finance lease liabilities represent obligations to make payments arising from the lease. Operating and finance lease assets represent the right to use an underlying asset for the lease term and are recognized at the lease commencement date based on the present value of the lease payments over the lease term. Leases with initial terms less than 12 months are not recognized as leases. For operating leases, an incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. For finance leases, the rate implicit in the lease, if known, is used to determine the present value of the lease payments. If the rate implicit in the lease is not known, the incremental borrowing rate, as determined at the lease commencement date, is used to determine the present value of the lease payments. Lease terms include options to extend or terminate the lease when it is reasonably certain that the option will be exercised. Operating lease expense is recognized on a straight-line basis over the expected lease term. Finance lease expense is comprised of depreciation and amortization, and interest expenses. Finance lease assets related to leased land for solar generation are amortized on a straight-line basis over the lease term, and are accounted for as operating leases for rate-making purposes. All other finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

NOTE 2. REGULATORY MATTERS

Regulatory Assets - Alliant Energy, IPL and WPL assess whether IPL’s and WPL’s regulatory assets are probable of future recovery by considering factors such as applicable regulations, recent orders by the applicable regulatory agencies, historical treatment of similar costs by the applicable regulatory agencies and regulatory environment changes. Based on these assessments, Alliant Energy, IPL and WPL believe the regulatory assets recognized as of December 31, 2023 are probable of future recovery. However, no assurance can be made that IPL and WPL will recover all of these regulatory assets in future rates. If future recovery of a regulatory asset ceases to be probable, the regulatory asset will be charged to expense. At December 31, regulatory assets were comprised of the following items (in millions):


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	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Tax-related	$934	$929	$831	$848	$103	$81
Pension and OPEB costs	347	392	171	197	176	195
Assets retired early	273	70	259	53	14	17
AROs	194	151	160	110	34	41
Commodity cost recovery	120	160	12	1	108	159
Derivatives	102	84	34	48	68	36
WPL’s Western Wisconsin gas distribution expansion investments	44	48	—	—	44	48
IPL’s DAEC PPA amendment	42	66	42	66	—	—

Other	205	146	68	63	137	83
	$2,261	$2,046	$1,577	$1,386	$684	$660

At December 31, 2023, IPL and WPL had $74 million and $32 million, respectively, of regulatory assets that were not earning a return on investment. IPL’s regulatory assets that were not earning a return consisted primarily of retired analog electric meters, emission allowances and costs for certain construction projects. WPL’s regulatory assets that were not earning a return consisted primarily of costs for certain construction projects. The other regulatory assets reported in the above table either earn a return or the cash has not yet been expended, in which case the assets are offset by liabilities that also do not incur a carrying cost.

Tax-related - IPL and WPL record regulatory assets for certain temporary differences (primarily related to utility property, plant and equipment at IPL) that result in a decrease in current rates charged to customers and an increase in future rates charged to customers based on the timing of income tax expense that is used to determine such rates. These temporary differences for IPL include the impacts of qualifying deductions for repairs expenditures, allocation of mixed service costs, and Iowa accelerated tax depreciation, which all contribute to lower current income tax expense during the first part of an asset’s useful life and higher current income tax expense during the latter part of an asset’s useful life. These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates. Refer to Note 12 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in 2023.

Pension and other postretirement benefits costs - The IUB, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates. These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs. Regulatory assets are also increased or decreased as a result of the annual defined benefit plan measurement process. Pension and OPEB costs are included within the recoverable cost of service component of rates charged to IPL’s and WPL’s retail and wholesale customers, which are based upon pension and OPEB costs determined in accordance with GAAP and are calculated in accordance with IPL’s and WPL’s respective regulatory jurisdictions.

Assets retired early - IPL and WPL have retired various natural gas- and coal-fired EGUs, and IPL has retired certain analog electric meters. As a result, the remaining net book value of these assets was reclassified from property, plant and equipment to a regulatory asset on their respective balance sheets. Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions):


Entity	Asset	Retirement Date	Regulatory Asset Balance as of Dec. 31, 2023	Recovery	Regulatory Approval
IPL	Lansing	2023	$216	Return of and return on remaining net book value through 2037	FERC and pending with the IUB (a)
IPL	Analog electric meters	2019	20	Return of remaining net book value through 2028	IUB and FERC
IPL	Sutherland Units 1 and 3	2017	12	Return of and return on remaining net book value through 2027	IUB and FERC
IPL	M.L. Kapp Unit 2	2018	11	Return of and return on remaining net book value through 2029	IUB and FERC

WPL	Edgewater Unit 4	2018	14	Return of and return on remaining net book value through 2028	PSCW and FERC

(a)IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request with the IUB for continued recovery of the remaining net book value of Lansing through 2037.


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AROs - Alliant Energy, IPL and WPL believe it is probable that certain differences between expenses accrued for AROs related to their utility operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets. In 2023, in conjunction with IPL's retirement of the Lansing Generating Station, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets.

Commodity cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s commodity cost recovery mechanisms. The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding. In 2021, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $37 million deferral as of December 31, 2022, which was collected in 2023 from its retail electric customers, plus interest. In 2022, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $117 million deferral as of December 31, 2022, which WPL is collecting from October 2023 through December 2025 from its retail electric customers, plus interest ($12 million was collected in 2023). In 2023, actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $34 million regulatory liability as of December 31, 2023, which is expected to be addressed in a future regulatory proceeding.

Derivatives - In accordance with IPL’s and WPL’s fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recoverable from customers in the future after any losses are realized, and gains from derivative instruments are refundable to customers in the future after any gains are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets. Refer to Note 15 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during 2023, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets.

WPL’s Western Wisconsin gas distribution expansion investments - WPL made contributions in aid of construction to a third party for investments as part of its Western Wisconsin gas distribution expansion project. Pursuant to authorization by the PSCW, Alliant Energy and WPL have recorded a regulatory asset for these costs, and are authorized by the PSCW to recover these amounts from WPL’s retail gas customers in base rates from 2021 through the end of 2040.

IPL’s DAEC PPA Amendment - In 2020, IPL made a buyout payment of $110 million in exchange for shortening the term of its DAEC PPA by 5 years. The buyout payment, including a return on, is being recovered from IPL’s retail and wholesale customers from 2021 through the end of 2025, and is currently being amortized to “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements.

Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Tax-related	$566	$579	$299	$303	$267	$276
Cost of removal obligations	366	398	242	259	124	139
Derivatives	65	210	34	115	31	95
Commodity cost recovery	48	40	13	38	35	2
WPL’s West Riverside liquidated damages	1	32	—	—	1	32




Other	84	65	56	39	28	26
	$1,130	$1,324	$644	$754	$486	$570

Tax-related regulatory liabilities reduce revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings. Cost of removal obligations, to the extent expensed through depreciation rates, reduce rate base. A significant portion of the remaining regulatory liabilities is not used to adjust revenue requirement calculations.

Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by the Tax Cuts and Jobs Act. The majority of these benefits related to accelerated depreciation are subject to tax normalization rules. These rules limit the rate at which these tax benefits are allowed to be passed on to customers.

Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated AROs or that have removal costs in addition to AROs. Alliant Energy, IPL and WPL record a regulatory liability for the amounts collected in rates for these future removal costs and reduce the regulatory liability for amounts spent on removal activities. Cash payments related to cost of removal obligations are included in “Other” in cash flows used for investing activities.

WPL’s West Riverside liquidated damages - Pursuant to terms included in the related West Riverside construction procurement contracts, WPL reached agreement with the contractor on liquidated damages in 2020. A significant portion of the liquidated damages was settled by WPL offsetting amounts owed to the contractor that were previously withheld for


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payment, which were non-cash investing activities. Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, resulting in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements in 2023.

Rate Reviews -

WPL’s Retail Electric and Gas Rate Reviews (2022/2023 Forward-looking Test Period) - In December 2021, the PSCW issued an order authorizing annual base rate increases of $114 million and $15 million for WPL’s retail electric and gas customers, respectively, covering the 2022/2023 forward-looking Test Period, which was based on a stipulated agreement between WPL and certain stakeholders. The key drivers for the annual base rate increases include higher retail fuel-related costs in 2022, lower excess deferred income tax benefits in 2022 and 2023 and revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation. In addition, the PSCW authorized WPL to receive a recovery of and a return on the remaining net book value of Edgewater Unit 5 through 2023. WPL's settlement extended, with certain modifications, an earnings sharing mechanism through 2023. Retail electric rate changes were effective on January 1, 2022 and extended through the end of 2023. Retail gas rate changes were effective on January 1, 2022 and extended through the end of 2022.

In December 2022, the PSCW issued an order authorizing an additional annual base rate increase of $9 million for WPL’s retail gas customers, covering the 2023 forward-looking Test Period, which reflects changes in weighted average cost of capital, updated depreciation rates and modifications to certain regulatory asset and regulatory liability amortizations. These retail gas rate changes were effective on January 1, 2023 and extended through the end of 2023.

WPL’s Retail Electric and Gas Rate Reviews (2024/2025 Forward-looking Test Period) - In December 2023, the PSCW issued an order authorizing annual base rate increases of $49 million and $13 million for WPL’s retail electric and gas customers, respectively, effective January 1, 2024, for the 2024 forward-looking Test Period. The PSCW’s order also authorized WPL to implement an additional $60 million increase in annual rates for its retail electric customers, effective January 1, 2025, for the 2025 forward-looking Test Period.

NOTE 3. PROPERTY, PLANT AND EQUIPMENT

At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Utility:
Electric plant:
Generation in service (a)	$9,180	$8,060	$5,025	$4,962	$4,155	$3,098
Distribution in service	7,314	6,912	4,091	3,876	3,223	3,036
Other in service	567	543	356	354	211	189
Anticipated to be retired early (b)	1,629	2,103	—	491	1,629	1,612
Total electric plant	18,690	17,618	9,472	9,683	9,218	7,935
Gas plant in service	1,791	1,705	951	910	840	795
Other plant in service	653	624	411	402	242	222
Accumulated depreciation (b)	(5,924)	(5,690)	(3,180)	(3,149)	(2,744)	(2,541)
Net plant	15,210	14,257	7,654	7,846	7,556	6,411
Leased Sheboygan Falls Energy Facility, net (c)	—	—	—	—	79	15
Leased land for solar generation, net	172	133	33	—	139	133
Construction work in progress	1,245	1,357	605	194	640	1,163
Other, net	7	6	6	6	1	—
Total utility	16,634	15,753	8,298	8,046	8,415	7,722
Non-utility and other:
Non-utility Generation, net (d)	68	71	—	—	—	—
Corporate Services and other, net (e)	455	423	—	—	—	—
Total non-utility and other	523	494	—	—	—	—
Total property, plant and equipment	$17,157	$16,247	$8,298	$8,046	$8,415	$7,722


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(a)Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding. Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $1,650/kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10%. Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred.

(b)In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets. In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively. WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026. Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023. WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023. As of December 31, 2023, net book values were $504 million for Edgewater Unit 5, and $428 million for Columbia Units 1 and 2 in aggregate.

(c)Less accumulated amortization of $112 million and $106 million for WPL as of December 31, 2023 and 2022, respectively. Refer to Note 10 for discussion of WPL’s renewal of this lease in 2023. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.

(d)Less accumulated depreciation of $75 million and $71 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

(e)Less accumulated depreciation of $275 million and $269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the income statements. The amount of AFUDC generated by equity and debt components was as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Equity	$74	$44	$18	$15	$8	$7	$59	$36	$11
Debt	26	16	7	6	3	2	20	13	5
	$100	$60	$25	$21	$11	$9	$79	$49	$16

Non-utility and Other - The non-utility and other property, plant and equipment recorded on Alliant Energy’s balance sheets include the following:

Non-utility Generation - The Sheboygan Falls Energy Facility was placed in service in 2005 and is depreciated using the straight-line method over a 35-year period.

Corporate Services and Other - Property, plant and equipment related to Corporate Services include a customer billing and information system for IPL and WPL and other computer software, and the corporate headquarters building located in Madison, Wisconsin. The customer billing and information system is amortized using the straight-line method over a 12-year period. The majority of the remaining software is amortized over a 5-year period. Other property, plant and equipment include Travero assets (a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; wind turbine blade recycling services; and a rail-served warehouse in Iowa). All Corporate Services and Other property, plant and equipment are depreciated using the straight-line method over periods ranging from 5 to 30 years.


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NOTE 4. JOINTLY-OWNED ELECTRIC UTILITY PLANT

Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):


	Ownership	Electric	Accumulated Provision	Construction
	Interest %	Plant	for Depreciation	Work in Progress
IPL
Ottumwa Unit 1	48.0%	$632	$264	$7
George Neal Unit 4	25.7%	196	107	6
George Neal Unit 3	28.0%	181	85	8
Louisa Unit 1	4.0%	44	22	—
		1,053	478	21
WPL
Columbia Units 1-2	53.5%	818	361	6
West Riverside Energy Center and Solar Facility (a)	73.8%	581	60	6
Forward Wind Energy Center	42.6%	118	53	—
		1,517	474	12
Alliant Energy		$2,570	$952	$33

(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.

NOTE 5. RECEIVABLES

NOTE 5(a) Accounts Receivable - Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Customer	$121	$114	$—	$—	$110	$102
Unbilled utility revenues	93	115	—	—	93	115
Deferred proceeds	216	185	216	185	—	—
Other	53	109	26	74	24	34
Allowance for expected credit losses	(8)	(7)	—	—	(8)	(7)
	$475	$516	$242	$259	$219	$244

In 2023, gross write-offs for accounts receivable were as follows (in millions):


	Originated in 2022	Originated in 2023
Alliant Energy	$12	$13
IPL	8	8
WPL	4	5

NOTE 5(b) Sales of Accounts Receivable - IPL maintains a Receivables Agreement whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The purchase commitment from the third party to which IPL sells its receivables expires in March 2024. IPL currently expects to amend and extend the purchase commitment. IPL pays a monthly fee to the third party that varies based on interest rates, limits on cash proceeds and cash amounts received from the third party. Deferred proceeds represent IPL’s interest in the receivables sold to the third party. At IPL’s request, deferred proceeds are paid to IPL from collections of receivables, after paying any required expenses incurred by the third party and the collection agent. Corporate Services acts as collection agent for the third party and receives a fee for collection services. The Receivables Agreement can be terminated by the third party if arrears or write-offs exceed certain levels. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. IPL believes that the allowance for expected credit losses related to its sales of receivables is a reasonable approximation of credit risk of the customers that generated the receivables. Refer to Note 16 for discussion of the fair value of deferred proceeds.

Under the Receivables Agreement, IPL has the right to receive cash proceeds, up to a certain limit, from the third party in exchange for the receivables sold. The limit on cash proceeds fluctuates between $5 million and $110 million, which IPL may change periodically throughout the year. As of December 31, 2023, the limit on cash proceeds was $5 million and IPL had


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$4 million of available capacity under its sales of accounts receivable program. Cash proceeds are used by IPL to meet short-term financing needs, and cannot exceed the current limit or amount of receivables available for sale, whichever is less. IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program were as follows (in millions):


	Maximum			Average
	2023	2022	2021	2023	2022	2021
Outstanding aggregate cash proceeds	$110	$80	$110	$51	$14	$46

As of December 31, the attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):


	2023	2022
Customer accounts receivable	$130	$145
Unbilled utility revenues	98	132
Other receivables	1	—
Receivables sold to third party	229	277
Less: cash proceeds	1	80
Deferred proceeds	228	197
Less: allowance for expected credit losses	12	12
Fair value of deferred proceeds	$216	$185
Outstanding receivables past due	$22	$26

Additional attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):


	2023	2022	2021
Collections	$2,233	$2,302	$2,134
Write-offs, net of recoveries	12	9	9

Effective January 2024, the limit on cash proceeds under the Receivables Agreement is $110 million.

NOTE 6. INVESTMENTS

Unconsolidated Equity Investments - Alliant Energy’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions):


	Ownership Interest at	Carrying Value at December 31,		Equity (Income) / Loss
	December 31, 2023	2023	2022	2023	2022	2021
ATC Holdings	16%, 20%	$386	$358	($49)	($41)	($43)
Non-utility wind farm in Oklahoma	50%	104	101	(7)	(5)	(4)
Corporate venture investments	Various	74	62	(2)	(3)	(13)
Other	Various	21	21	(3)	(2)	(2)
		$585	$542	($61)	($51)	($62)

Summary aggregate financial information from the financial statements of these holdings is as follows (in millions):


	Alliant Energy
	2023	2022	2021
Revenues	$898	$813	$802
Operating income	384	350	357
Net income	370	675	358
As of December 31:
Current assets	221	227
Non-current assets	9,032	8,292
Current liabilities	528	620
Non-current liabilities	3,584	3,285
Noncontrolling interest	259	289

ATC Holdings - As of December 31, 2023, Alliant Energy has a 16% ownership interest in ATC and a 20% ownership interest in ATC Holdco LLC, collectively referred to as ATC Holdings. ATC is an independent, for-profit, transmission-only company. ATC Holdco LLC holds Duke-American Transmission Company, LLC, a joint venture between Duke Energy Corporation and ATC, that owns electric transmission infrastructure in North America. Refer to Note 17(g) for discussion of a reduction in earnings recorded in 2022 related to a court decision, which is currently expected to reduce the base return on equity authorized for MISO transmission owners, including ATC.


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Non-utility Wind Farm in Oklahoma - The non-utility wind farm located in Oklahoma provides electricity to a third-party under a long-term PPA, and has both cash and tax equity ownership. Alliant Energy does not maintain or operate the wind farm, and provided a parent guarantee of its subsidiary’s indemnification obligations under the operating agreement and PPA. Refer to Note 17(d) for discussion of the guarantee.

Corporate Venture Investments - Alliant Energy has various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy.

NOTE 7. COMMON EQUITY

Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:


	2023	2022	2021
Shares outstanding, January 1	251,134,966	250,474,529	249,868,415

At-the-market offering program	4,372,561	—	—
Shareowner Direct Plan	454,987	437,669	492,565
Equity-based compensation plans	134,334	222,768	113,549

Shares outstanding, December 31	256,096,848	251,134,966	250,474,529

At December 31, 2023, Alliant Energy had a total of 13 million shares available for issuance in the aggregate, pursuant to its 2020 OIP, Shareowner Direct Plan and 401(k) Savings Plan.

At-the-Market Offering Program - In December 2022, Alliant Energy filed a prospectus supplement to sell up to $225 million of its common stock through an at-the-market offering program. As of December 31, 2023, Alliant Energy issued 4,372,561 shares of common stock through this program and received cash proceeds of $223 million, net of $2 million in commissions and fees. The proceeds from the issuances of common stock were used for general corporate purposes. This at-the-market offering program has expired.

Shareowner Direct Plan - Alliant Energy satisfies its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market.

NOTE 8. PREFERRED STOCK

In 2021, IPL redeemed all 8,000,000 outstanding shares of its 5.1% cumulative preferred stock at the $25 per share par value for $200 million plus accrued and unpaid dividends up to the redemption date. In 2021, Alliant Energy and IPL recorded a $5 million non-cash charge related to this transaction in “Preferred dividend requirements” in their income statements.

NOTE 9. DEBT

NOTE 9(a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding. At December 31, 2023, the short-term borrowing capacity under a single credit facility agreement totaled $1 billion ($450 million for Alliant Energy at the parent company level, $150 million for IPL and $400 million for WPL). Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $500 million, $400 million and $500 million, respectively, within the $1 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions):


	Alliant Energy		IPL		WPL
December 31	2023	2022	2023	2022	2023	2022
Amount outstanding	$475	$642	$—	$—	$318	$290
Weighted average interest rates	5.5%	4.6%	N/A	N/A	5.4%	4.5%
Available credit facility capacity	$525	$358	$150	$100	$82	$110


	Alliant Energy		IPL		WPL
For the year ended	2023	2022	2023	2022	2023	2022
Maximum amount outstanding (based on daily outstanding balances)	$793	$665	$70	$—	$349	$325
Average amount outstanding (based on daily outstanding balances)	$386	$411	$2	$—	$157	$153
Weighted average interest rates	5.2%	2.1%	5.3%	—%	5.1%	1.6%

In January 2024, Alliant Energy, IPL and WPL extended their single credit facility agreement, which currently expires in December 2028, and reallocated credit facility capacity amounts to $350 million for Alliant Energy at the parent company level, $150 million for IPL and $500 million for WPL, within the $1 billion total commitment.


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NOTE 9(b) Long-Term Debt - Long-term debt, net as of December 31 was as follows (dollars in millions):


	2023			2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Senior Debentures (a):
3.25%, due 2024	$500	$500	$—	$500	$500	$—
3.4%, due 2025	250	250	—	250	250	—
5.5%, due 2025	50	50	—	50	50	—
4.1%, due 2028	500	500	—	500	500	—
3.6%, due 2029	300	300	—	300	300	—
2.3%, due 2030	400	400	—	400	400	—
5.7%, due 2033 (b)	300	300	—	—	—	—
6.45%, due 2033	100	100	—	100	100	—
6.3%, due 2034	125	125	—	125	125	—
6.25%, due 2039	300	300	—	300	300	—
4.7%, due 2043	250	250	—	250	250	—
3.7%, due 2046	300	300	—	300	300	—
3.5%, due 2049	300	300	—	300	300	—
3.1%, due 2051	300	300	—	300	300	—
	3,975	3,975	—	3,675	3,675	—
Debentures (a):
3.05%, due 2027	300	—	300	300	—	300
3%, due 2029	350	—	350	350	—	350
1.95%, due 2031	300	—	300	300	—	300
3.95%, due 2032	600	—	600	600	—	600
4.95% due 2033 (c)	300	—	300	—	—	—
6.25%, due 2034	100	—	100	100	—	100
6.375%, due 2037	300	—	300	300	—	300
7.6%, due 2038	250	—	250	250	—	250
4.1%, due 2044	250	—	250	250	—	250
3.65%, due 2050	350	—	350	350	—	350
	3,100	—	3,100	2,800	—	2,800
Other:
AEF term loan credit agreement through March 2024, 6% at December 31, 2023 (with Alliant Energy as guarantor) (d)	300	—	—	400	—	—
AEF 1.4% senior notes, due 2026 (with Alliant Energy as guarantor) (a)	200	—	—	200	—	—
Alliant Energy 3.875% convertible senior notes, due 2026 (e)	575	—	—	—	—	—
AEF 4.25% senior notes, due 2028 (with Alliant Energy as guarantor) (a)	300	—	—	300	—	—
AEF 5.95% senior notes, due 2029 (with Alliant Energy as guarantor) (a)(f)	300	—	—	—	—	—
AEF 3.6% senior notes, due 2032 (with Alliant Energy as guarantor) (a)	350	—	—	350	—	—
Sheboygan Power, LLC 5.06% senior secured notes, due 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a)	9	—	—	17	—	—


AEF 3.75% senior notes (with Alliant Energy as guarantor) (Retired in 2023)	—	—	—	400	—	—
Other, 1% at December 31, 2023, due 2024 to 2025	—	—	—	1	—	—
	2,034	—	—	1,668	—	—
Subtotal	9,109	3,975	3,100	8,143	3,675	2,800
Current maturities	(809)	(500)	—	(408)	—	—
Unamortized debt issuance costs	(54)	(21)	(19)	(45)	(21)	(19)
Unamortized debt (discount) and premium, net	(21)	(9)	(11)	(22)	(8)	(11)
Long-term debt, net (g)	$8,225	$3,445	$3,070	$7,668	$3,646	$2,770

(a)Contains optional redemption provisions which, if elected by the issuer at its sole discretion, could require material redemption premium payments by the issuer. The redemption premium payments under these optional redemption provisions are variable and dependent on applicable U.S. Treasury rates at the time of redemption.

(b)In September 2023, IPL issued $300 million of 5.7% senior debentures due 2033. The net proceeds from the issuance were used to reduce cash amounts received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt, for general corporate purposes and/or were placed in money market fund investments.


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(c)In March 2023, WPL issued $300 million of 4.95% debentures due 2033. The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds was disbursed for the development and acquisition of its solar EGUs.

(d)In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026 to mitigate interest rate risk. Under the terms of the swap, AEF exchanged a variable interest rate for a fixed interest rate of 3.93% on a portion of its variable-rate term loan borrowings. In December 2023, AEF retired the remaining $100 million variable-rate term loan borrowings. Refer to Note 15 for additional information on the interest rate swap.

(e)Refer to “Convertible Senior Notes” below for additional information.

(f)In November 2023, AEF issued $300 million of 5.95% senior notes due 2029. The net proceeds from AEF’s issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes.

(g)There were no significant sinking fund requirements related to the outstanding long-term debt.

Convertible Senior Notes - In March 2023, Alliant Energy issued $575 million of 3.875% convertible senior notes (the Notes), which are senior unsecured obligations, and used the net proceeds from the issuance for general corporate purposes. The Notes will mature on March 15, 2026 unless earlier converted or repurchased. Alliant Energy may not redeem the Notes prior to the maturity date. Holders may convert their Notes at their option at any time prior to the close of business on the business day immediately preceding December 15, 2025 only under the following circumstances:

during any calendar quarter commencing after the calendar quarter ending on June 30, 2023 (and only during such calendar quarter), if the last reported sale price of Alliant Energy’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day during such period;
during the 5 business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $1,000 principal amount of Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of Alliant Energy’s common stock and the conversion rate on each such trading day; or
upon the occurrence of specified corporate events.

On or after December 15, 2025 until the close of business on the business day immediately preceding the maturity date, holders may convert all or any portion of their Notes at any time, regardless of the foregoing circumstances. Upon conversion of the Notes, Alliant Energy will pay cash up to the aggregate principal amount of the Notes to be converted and pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the Notes being converted.

The initial conversion rate is 15.5461 shares of common stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of approximately $64.32 per share of Alliant Energy’s common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, Alliant Energy will, in certain circumstances, increase the conversion rate for a holder who elects to convert its Notes in connection with such a corporate event.

If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the Notes may require Alliant Energy to repurchase for cash all or any portion of its Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

As of December 31, 2023, the conditions allowing holders of the Notes to convert their Notes were not met, and as a result, the Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet. As of December 31, 2023, the net carrying amount of the Notes was $568 million, with unamortized debt issuance costs of $7 million, and the estimated fair value (Level 2) of the Notes was $572 million. As of December 31, 2023, there were no shares of Alliant Energy’s common stock related to the potential conversion of the Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the Notes.

Five-Year Schedule of Long-term Debt Maturities - At December 31, 2023, long-term debt maturities for 2024 through 2028 were as follows (in millions):


	2024	2025	2026	2027	2028
IPL	$500	$300	$—	$—	$500
WPL	—	—	—	300	—

AEF	309	—	200	—	300
Alliant Energy parent company	—	—	575	—	—
Alliant Energy	$809	$300	$775	$300	$800


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Fair Value of Long-term Debt - Refer to Note 16 for information on the fair value of long-term debt outstanding.

NOTE 10. LEASES

Operating Leases - Alliant Energy’s, IPL’s and WPL’s operating leases primarily include leases of space on telecommunication towers and leases of property. Operating lease details are as follows (dollars in millions):


	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net	$23	$13	$9	$16	$9	$6
Other current liabilities	$2	$1	$1	$3	$1	$1
Other liabilities	21	12	8	13	8	5
Total operating lease liabilities	$23	$13	$9	$16	$9	$6
Weighted average remaining lease term	12 years	12 years	12 years	10 years	11 years	9 years
Weighted average discount rate	4%	4%	4%	4%	4%	4%

Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business. WPL is responsible for the operation of the EGU and has exclusive rights to its output. In 2023, WPL renewed this financing lease through 2039. This lease contains one remaining lease renewal period, which is not included in the finance lease obligation. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below.

Related to their investments in solar generation, IPL and WPL entered into various land lease agreements with unaffiliated parties that have commenced. The leases have various terms with optional renewal periods that are assumed to be extended through the end of the estimated useful lives of the solar generating facilities. The leases do not contain purchase options and are fixed lease payments.

Finance lease details are as follows (dollars in millions):


	December 31, 2023			December 31, 2022
	Alliant Energy	IPL	WPL	Alliant Energy	IPL	WPL
Property, plant and equipment, net:
Sheboygan Falls Energy Facility	N/A	N/A	$79	N/A	N/A	$15
Leased land for solar generation	$172	$33	139	$133	$—	133
	$172	$33	$218	$133	$—	$148
Other current liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	$11	N/A	N/A	$12
Leased land for solar generation	$—	$—	—	$5	$—	5
	—	—	11	5	—	17
Other liabilities:
Sheboygan Falls Energy Facility	N/A	N/A	78	N/A	N/A	19
Leased land for solar generation	172	33	139	131	—	131
	172	33	217	131	—	150
Total finance lease liabilities	$172	$33	$228	$136	$—	$167
Weighted average remaining lease term	33 years	29 years	27 years	34 years	N/A	28 years
Weighted average discount rate	5%	5%	5%	5%	N/A	5%


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Depreciation and amortization expenses	$1	$—	$—	$—	$—	$—	$6	$6	$6
Interest expense	6	3	—	1	—	—	8	7	5
Total finance lease expense	$7	$3	$—	$1	$—	$—	$14	$13	$11

Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022		2023	2022	2023	2022
Finance lease liabilities arising from obtaining leased assets	$34	$125		$33	$—	$71	$125


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Expected Maturities - As of December 31, 2023, expected maturities of lease liabilities were as follows (in millions):


	2024	2025	2026	2027	2028	Thereafter	Total	Less: amount representing interest	Present value of minimum lease payments
Operating Leases:
Alliant Energy	$3	$3	$3	$3	$2	$16	$30	$7	$23
IPL	1	2	2	1	1	10	17	4	13
WPL	2	1	1	1	1	6	12	3	9
Finance Leases:
Alliant Energy	8	8	8	8	8	320	360	188	172
IPL	2	2	2	2	2	59	69	36	33
WPL	21	17	13	13	13	334	411	183	228

NOTE 11. REVENUES

Revenues from Alliant Energy’s, IPL’s and WPL’s utility businesses are primarily from electric and gas sales provided to customers based on approved tariffs or specific contracts with customers. IPL’s and WPL’s primary performance obligations under such arrangements are to deliver electricity and gas, and their customers simultaneously receive and consume the electricity and gas. For such arrangements, revenues are recognized equivalent to the value of the electricity or gas supplied during each period, including amounts billed during each period and changes in amounts estimated to be billed at the end of each period. IPL and WPL apply the right to invoice method to measure progress towards completing performance obligations to transfer electricity and gas to their customers.

IPL provides retail electric and gas service to customers in Iowa, and WPL provides retail and wholesale electric and retail gas service to customers in Wisconsin. IPL also provides electricity to wholesale customers in Minnesota, Illinois and Iowa, as well as steam from its Prairie Creek Generating Station to high-pressure steam customers in Iowa.

IPL’s and WPL’s retail electric and gas revenues include sales to residential, commercial and industrial customers. IPL’s and WPL’s retail electric and gas customer prices are based on IPL’s and WPL’s cost of service and are determined through general rate review proceedings and various tariff filings with the IUB and PSCW, respectively. Such tariff-based services provide electricity or gas to customers without a defined contractual term.

IPL and WPL have wholesale electric market-based rate authority from FERC allowing them to participate in wholesale energy markets (e.g. MISO) and transact directly with third parties. This authority from FERC allows sales of electricity referred to as bulk power sales based on current market values. FERC also allows IPL and WPL to enter into power supply agreements with municipalities and rural electric cooperatives with defined contractual terms, which include standard pricing mechanisms that are detailed in current tariffs accepted by FERC through wholesale rate review proceedings.

Revenues from Alliant Energy’s non-utility business customers are primarily from its Travero business, which includes a short-line rail freight service in Iowa; a Mississippi River barge, rail and truck freight terminal in Illinois; freight brokerage services; and a rail-served warehouse in Iowa.


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Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Electric Utility:
Retail - residential	$1,220	$1,233	$1,115	$641	$673	$620	$579	$560	$495
Retail - commercial	820	821	763	519	536	508	301	285	255
Retail - industrial	968	965	893	501	538	505	467	427	388
Wholesale	213	233	187	62	64	57	151	169	130
Bulk power and other	124	169	123	38	48	62	86	121	61
Total Electric Utility	3,345	3,421	3,081	1,761	1,859	1,752	1,584	1,562	1,329
Gas Utility:
Retail - residential	316	371	257	176	202	146	140	169	111
Retail - commercial	163	197	139	86	101	79	77	96	60
Retail - industrial	16	20	17	11	14	12	5	6	5
Transportation/other	45	54	43	27	34	28	18	20	15
Total Gas Utility	540	642	456	300	351	265	240	291	191
Other Utility:
Steam	45	39	36	45	39	36	—	—	—
Other utility	7	10	13	4	7	10	3	3	3
Total Other Utility	52	49	49	49	46	46	3	3	3
Non-Utility and Other:

Travero and other	90	93	83	—	—	—	—	—	—
Total Non-Utility and Other	90	93	83	—	—	—	—	—	—
Total revenues	$4,027	$4,205	$3,669	$2,110	$2,256	$2,063	$1,827	$1,856	$1,523

NOTE 12. INCOME TAXES

Income Tax Expense (Benefit) - The components of “Income tax expense (benefit)” in the income statements were as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Current tax expense (benefit):
Federal	($3)	$7	$1	($44)	($29)	($21)	$48	$46	$22
State	(6)	2	3	(21)	(8)	(1)	25	16	6

Deferred tax expense (benefit):
Federal	100	109	9	87	91	73	10	10	(75)
State	36	28	15	17	1	—	3	12	11
Production tax credits	(121)	(123)	(101)	(95)	(105)	(87)	(26)	(18)	(14)
Investment tax credits	(1)	(1)	(1)	(1)	—	—	—	—	(1)



Provision recorded as a change in accrued interest	(1)	—	—	(1)	—	—	—	—	—
	$4	$22	($74)	($58)	($50)	($36)	$60	$66	($51)


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Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Statutory federal income tax rate	21%	21%	21%	21%	21%	21%	21%	21%	21%
State income taxes, net of federal benefits	2	3	2	(2)	(2)	(1)	5	6	6
Production tax credits	(17)	(18)	(17)	(31)	(34)	(27)	(7)	(5)	(6)
Amortization of excess deferred taxes (Refer to Note 2)	(2)	(2)	(18)	(2)	(2)	(4)	(2)	(3)	(43)
Effect of rate-making on property-related differences	(4)	(1)	(1)	(5)	(1)	(2)	(3)	(2)	(1)
Adjustment for prior period taxes	—	1	1	—	1	2	—	—	—


Other items, net	1	(1)	—	—	1	—	1	—	(1)
Overall income tax rate	1%	3%	(12%)	(19%)	(16%)	(11%)	15%	17%	(24%)

Deferred Tax Assets and Liabilities - The deferred tax assets and liabilities included on the balance sheets at December 31 arise from the following temporary differences (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Deferred tax liabilities:
Property	$2,453	$2,442	$1,415	$1,440	$972	$938
ATC Holdings	127	125	—	—	—	—
Other	213	155	157	86	64	80
Total deferred tax liabilities	2,793	2,722	1,572	1,526	1,036	1,018
Deferred tax assets:
Federal credit carryforwards	649	672	449	450	191	209

Net operating losses carryforwards - state	26	32	1	—	—	—
Other	79	75	32	29	19	20
Subtotal deferred tax assets	754	779	482	479	210	229
Valuation allowances	(3)	—	(1)	—	(1)	—
Total deferred tax assets	751	779	481	479	209	229
Total deferred tax liabilities, net	$2,042	$1,943	$1,091	$1,047	$827	$789

Carryforwards - At December 31, 2023, carryforwards and expiration dates were estimated as follows (in millions):


	Range of Expiration Dates	Alliant Energy	IPL	WPL

State net operating losses	2025-2043	$428	$6	$1
Federal tax credits	2031-2043	649	449	191

Valuation Allowances - Refer to N ote 1 (c) for discussion of valuation allowances recorded in 2023 related to the expected transfer of renewable tax credits to other corporate taxpayers.

Uncertain Tax Positions - At December 31, 2023, 2022 and 2021, there were no uncertain tax positions or penalties accrued related to uncertain tax positions. As of December 31, 2023, no material changes to unrecognized tax benefits are expected during the next 12 months.

Open tax years - Tax years that remain subject to the statute of limitations in the major jurisdictions for each of Alliant Energy, IPL and WPL are as follows:


Consolidated federal income tax returns (a)	2019	-	2022
Consolidated Iowa income tax returns (b)	2020	-	2022
Wisconsin combined tax returns (c)	2019	-	2022

(a)The 2020 and 2021 federal tax returns are effectively settled as a result of participation in the IRS Compliance Assurance Program, which allows Alliant Energy and the IRS to work together to resolve issues related to Alliant Energy’s current tax year before filing its federal income tax return. The statute of limitations for these federal tax returns expires three years from each filing date.

(b)The statute of limitations for these Iowa tax returns expires three years from each filing date.

(c)The statute of limitations for these Wisconsin combined tax returns expires four years from each filing date.


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Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12% to 9.8%, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior.

In March 2022, additional Iowa tax reform was enacted. Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied. These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5%, compared to the 9.8% Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted. In September 2022 and September 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4% effective January 1, 2023, and 7.1% effective January 1, 2024, respectively. Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled. Given the announcements of the new Iowa corporate income tax rates, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured in 2022 and 2023 based upon the new rates effective January 1, 2023 and January 1, 2024, which resulted in a $77 million and $74 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2022 and 2023, respectively. The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future. Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rates effective January 1, 2023 and January 1, 2024, which resulted in charges of $8 million and $10 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred income tax liabilities on Alliant Energy’s balance sheets in 2022 and 2023, respectively. Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.

NOTE 13. BENEFIT PLANS

NOTE 13(a) Pension and Other Postretirement Benefits Plans - Retirement benefits are provided to substantially all employees through various qualified and non-qualified non-contributory defined benefit pension plans (currently closed to new hires), and/or through defined contribution plans (including 401(k) savings plans). Benefits of the non-contributory defined benefit pension plans are based on the plan participant’s years of service, age and compensation. Benefits of the defined contribution plans are based on the plan participant’s years of service, age, compensation and contributions. Certain defined benefit postretirement health care and life benefits are provided to eligible retirees. In general, the retiree health care plans consist of fixed benefit subsidy structures and the retiree life insurance plans are non-contributory.

IPL and WPL account for their participation in Alliant Energy and Corporate Services sponsored plans as multiple-employer plans. For IPL and WPL, amounts below represent the amounts for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.

Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows:


	Defined Benefit Pension Plans									OPEB Plans
Alliant Energy	2023			2022			2021			2023	2022	2021
Discount rate for benefit obligations	5.36%			5.54%			2.91%			5.40%	5.53%	2.81%
Discount rate for net periodic cost	5.54%			2.91%			2.57%			5.53%	2.81%	2.31%
Expected rate of return on plan assets	7.80%			7.80%			7.10%			6.50%	6.40%	4.80%
Interest crediting rate for Alliant Energy Cash Balance Pension Plan	10.75%			9.22%			4.18%			N/A	N/A	N/A
Rate of compensation increase	3.30%	-	4.50%	3.30%	-	4.50%	3.30%	-	4.50%	N/A	N/A	N/A


	Qualified Defined Benefit Pension Plan			OPEB Plans
IPL	2023	2022	2021	2023	2022	2021
Discount rate for benefit obligations	5.35%	5.55%	2.94%	5.40%	5.53%	2.80%
Discount rate for net periodic cost	5.55%	2.94%	2.61%	5.53%	2.80%	2.28%
Expected rate of return on plan assets	7.80%	7.80%	7.10%	6.90%	6.50%	5.10%
Rate of compensation increase	3.30%	3.30%	3.30%	N/A	N/A	N/A


	Qualified Defined Benefit Pension Plan			OPEB Plans
WPL	2023	2022	2021	2023	2022	2021
Discount rate for benefit obligations	5.35%	5.54%	2.94%	5.40%	5.53%	2.79%
Discount rate for net periodic cost	5.54%	2.94%	2.64%	5.53%	2.79%	2.27%
Expected rate of return on plan assets	7.80%	7.80%	7.10%	5.65%	5.49%	4.02%
Rate of compensation increase	3.30%	3.30%	3.30%	N/A	N/A	N/A


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Expected rate of return on plan assets - The expected rate of return on plan assets is based on projected asset class returns using target allocations. A forward-looking building blocks approach is used, and historical returns, survey information and capital market information are analyzed to support the expected rate of return on plan assets assumption. Refer to “Investment Strategy for Plan Assets” below for additional information related to investment strategy and mix of assets for the pension and OPEB plans.

Life Expectancy - The life expectancy assumption is used in determining the benefit obligation and net periodic benefit cost for defined benefit pension and OPEB plans. This assumption utilizes base mortality tables that were released in 2019 by the Society of Actuaries and mortality projection tables that were released in 2021 by the Society of Actuaries.

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans are included below (in millions). The service cost component of net periodic benefit costs is included in “Other operation and maintenance” expenses in the income statements and all other components of net periodic benefit costs are included in “Other (income) and deductions” in the income statements or regulatory assets on the balance sheets.


Alliant Energy	Defined Benefit Pension Plans						OPEB Plans
2023		2022		2021		2023		2022		2021
Service cost	$5		$9		$11		$2		$3		$4
Interest cost	47		36		34		9		6		5
Expected return on plan assets (a)	(53)		(69)		(69)		(5)		(5)		(5)
Amortization of prior service credit (b)	(1)		(1)		—		—		—		—
Amortization of actuarial loss (c)	28		32		39		1		2		5
Settlement losses (d)	—		26		—		—		—		—
	$26		$33		$15		$7		$6		$9


IPL	Defined Benefit Pension Plans						OPEB Plans
2023		2022		2021		2023		2022		2021
Service cost	$3		$6		$7		$1		$1		$1
Interest cost	21		16		16		3		2		2
Expected return on plan assets (a)	(26)		(31)		(32)		(3)		(4)		(3)

Amortization of actuarial loss (c)	11		13		17		1		1		2
Settlement losses (d)	—		13		—		—		—		—
	$9		$17		$8		$2		$—		$2


WPL	Defined Benefit Pension Plans						OPEB Plans
2023		2022		2021		2023		2022		2021
Service cost	$2		$3		$4		$1		$1		$1
Interest cost	20		16		15		3		2		2
Expected return on plan assets (a)	(22)		(31)		(31)		(1)		(1)		—

Amortization of actuarial loss (c)	13		15		19		1		2		2
Settlement losses (d)	—		13		—		—		—		—
	$13		$16		$7		$4		$4		$5

(a)The expected return on plan assets is based on the expected rate of return on plan assets and the fair value approach to the market-related value of plan assets.

(b)Unrecognized prior service credits for the OPEB plans are amortized over the average future service period to full eligibility of the participants of each plan.

(c)Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits.

(d)Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans. In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan.


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Benefit Plan Assets and Obligations - A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions):


	Defined Benefit Pension Plans		OPEB Plans
Alliant Energy	2023	2022	2023	2022
Change in benefit obligation:
Net benefit obligation at January 1	$875	$1,251	$168	$210
Service cost	5	9	2	3
Interest cost	47	36	9	6
Plan participants’ contributions	—	—	4	4


Actuarial (gain) loss	23	(269)	(3)	(37)

Gross benefits paid	(74)	(152)	(20)	(18)

Net benefit obligation at December 31	876	875	160	168
Change in plan assets:
Fair value of plan assets at January 1	706	1,011	83	106
Actual return on plan assets	86	(204)	8	(17)
Employer contributions	14	51	8	8
Plan participants’ contributions	—	—	4	4
Gross benefits paid	(74)	(152)	(20)	(18)
Fair value of plan assets at December 31	732	706	83	83
Under funded status at December 31	($144)	($169)	($77)	($85)


	Defined Benefit Pension Plans		OPEB Plans
Alliant Energy	2023	2022	2023	2022
Amounts recognized on the balance sheets consist of:
Non-current assets	$—	$—	$14	$9
Current liabilities	(2)	(2)	(8)	(8)
Pension and other benefit obligations	(142)	(167)	(83)	(86)
Net amounts recognized at December 31	($144)	($169)	($77)	($85)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	$337	$376	$11	$20
Prior service credit	(2)	(3)	—	—
	$335	$373	$11	$20


	Defined Benefit Pension Plans		OPEB Plans
IPL	2023	2022	2023	2022
Change in benefit obligation:
Net benefit obligation at January 1	$389	$567	$68	$84
Service cost	3	6	1	1
Interest cost	21	16	3	2
Plan participants’ contributions	—	—	2	2


Actuarial (gain) loss	9	(123)	(1)	(14)

Gross benefits paid	(35)	(77)	(8)	(7)

Net benefit obligation at December 31	387	389	65	68
Change in plan assets:
Fair value of plan assets at January 1	344	462	58	74
Actual return on plan assets	42	(92)	7	(12)
Employer contributions	1	51	2	1
Plan participants’ contributions	—	—	2	2
Gross benefits paid	(35)	(77)	(8)	(7)
Fair value of plan assets at December 31	352	344	61	58
Under funded status at December 31	($35)	($45)	($4)	($10)


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	Defined Benefit Pension Plans		OPEB Plans
IPL	2023	2022	2023	2022
Amounts recognized on the balance sheets consist of:
Non-current assets	$—	$—	$10	$6
Current liabilities	—	—	(1)	(2)
Pension and other benefit obligations	(35)	(45)	(13)	(14)
Net amounts recognized at December 31	($35)	($45)	($4)	($10)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	$135	$154	$9	$14
Prior service credit	(1)	(1)	—	—
	$134	$153	$9	$14


	Defined Benefit Pension Plans		OPEB Plans
WPL	2023	2022	2023	2022
Change in benefit obligation:
Net benefit obligation at January 1	$381	$546	$65	$81
Service cost	2	3	1	1
Interest cost	20	16	3	2
Plan participants’ contributions	—	—	2	2


Actuarial (gain) loss	10	(117)	(2)	(13)

Gross benefits paid	(32)	(67)	(8)	(8)

Net benefit obligation at December 31	381	381	61	65
Change in plan assets:
Fair value of plan assets at January 1	291	450	14	17
Actual return on plan assets	35	(92)	1	(2)
Employer contributions	12	—	5	5
Plan participants’ contributions	—	—	2	2
Gross benefits paid	(32)	(67)	(8)	(8)
Fair value of plan assets at December 31	306	291	14	14
Under funded status at December 31	($75)	($90)	($47)	($51)


	Defined Benefit Pension Plans		OPEB Plans
WPL	2023	2022	2023	2022
Amounts recognized on the balance sheets consist of:
Non-current assets	$—	$—	$4	$3
Current liabilities	—	—	(6)	(5)
Pension and other benefit obligations	(75)	(90)	(45)	(49)
Net amounts recognized at December 31	($75)	($90)	($47)	($51)
Amounts recognized in Regulatory Assets consist of:
Net actuarial loss	$148	$165	$3	$6
Prior service credit	—	—	—	—
	$148	$165	$3	$6

In 2023, actuarial losses related to benefit obligations for defined benefit pension plans were primarily due to decreases in the discount rates. In 2022, actuarial gains related to benefit obligations for defined benefit pension and OPEB plans were primarily due to increases in the discount rates.


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Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions):


	Defined Benefit Pension Plans		OPEB Plans
Alliant Energy	2023	2022	2023	2022
Accumulated benefit obligations	$857	$857	$160	$168
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	857	857	160	168
Fair value of plan assets	732	706	83	83
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	876	875	N/A	N/A
Fair value of plan assets	732	706	N/A	N/A


	Defined Benefit Pension Plans		OPEB Plans
IPL	2023	2022	2023	2022
Accumulated benefit obligations	$377	$379	$65	$68
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	377	379	65	68
Fair value of plan assets	352	344	61	58
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	387	389	N/A	N/A
Fair value of plan assets	352	344	N/A	N/A


	Defined Benefit Pension Plans		OPEB Plans
WPL	2023	2022	2023	2022
Accumulated benefit obligations	$373	$373	$61	$65
Plans with accumulated benefit obligations in excess of plan assets:
Accumulated benefit obligations	373	373	61	65
Fair value of plan assets	306	291	14	14
Plans with projected benefit obligations in excess of plan assets:
Projected benefit obligations	381	381	N/A	N/A
Fair value of plan assets	306	291	N/A	N/A

In addition to the amounts recognized in regulatory assets in the above tables for IPL and WPL, regulatory assets were recognized for amounts associated with Corporate Services employees participating in other Alliant Energy sponsored benefit plans that were allocated to IPL and WPL at December 31 as follows (in millions):


	IPL		WPL
	2023	2022	2023	2022
Regulatory assets	$28	$30	$24	$25

Estimated Future Employer Contributions and Benefit Payments - Estimated funding for the qualified and non-qualified defined benefit pension and OPEB plans for 2024 is as follows (in millions):


	Alliant Energy	IPL	WPL
Defined benefit pension plans (a)	$12	$—	$10
OPEB plans	8	1	6

(a)Alliant Energy sponsors several non-qualified defined benefit pension plans that cover certain current and former key employees of IPL and WPL. Alliant Energy allocates pension costs to IPL and WPL for these plans. In addition, IPL and WPL amounts reflect funding for their non-bargaining employees who are participants in the Alliant Energy and Corporate Services sponsored qualified and non-qualified defined benefit pension plans.

Expected benefit payments for the qualified and non-qualified defined benefit plans, which reflect expected future service, as appropriate, are as follows (in millions):


Alliant Energy	2024	2025	2026	2027	2028	2029 - 2033
Defined benefit pension benefits	$73	$73	$74	$75	$75	$343
OPEB	17	17	16	16	15	65
	$90	$90	$90	$91	$90	$408


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IPL	2024	2025	2026	2027	2028	2029 - 2033
Defined benefit pension benefits	$34	$34	$34	$33	$33	$151
OPEB	7	7	7	6	6	25
	$41	$41	$41	$39	$39	$176


WPL	2024	2025	2026	2027	2028	2029 - 2033
Defined benefit pension benefits	$32	$32	$31	$31	$31	$146
OPEB	7	7	6	6	6	24
	$39	$39	$37	$37	$37	$170

Investment Strategy for Plan Assets - Investment strategies for defined benefit pension and OPEB plan assets combine preservation of principal and prudent risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term. Investment risk of plan assets is mitigated through diversification, including equity, fixed income and global asset strategies. Global asset strategies may include investments in global equity, global debt and currencies.

Defined Benefit Pension Plan Assets - The asset mix of defined benefit pension plans is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. An overlay management service is also used to help maintain target allocations and meet liquidity needs. The overlay manager is authorized to use derivative financial instruments to facilitate this service. For separately managed accounts, prohibited investments include, but are not limited to, direct ownership of real estate, oil and gas limited partnerships, securities of the managers’ firms or affiliate firms, and Alliant Energy securities. The allocations shown below exclude market exposure obtained through the overlay management service. At December 31, 2023, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows:


	Target Range			Actual
	Allocation			Allocation
Cash and equivalents	0%	-	5%	2%
Equity securities	47%	-	67%	56%

Global asset securities	0%	-	15%	5%

Fixed income securities	27%	-	47%	37%

Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts. For VEBA trusts with assets greater than $5 million and the WPL 401(h) assets, the mix among asset classes is governed by allocation targets. The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges. At December 31, 2023, the current target ranges and actual allocations for VEBA trusts with assets greater than $5 million and the WPL 401(h) assets were as follows:


	Target Range			Actual
	Allocation			Allocation
Cash and equivalents	0%	-	5%	1%
Equity securities	0%	-	55%	36%


Fixed income securities	40%	-	100%	63%

Fair Value Measurements - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Refer to Note 16 for discussion of levels within the fair value hierarchy. Level 1 items include investments in securities held in registered investment companies and directly held equity securities, which are valued at the closing price reported in the active market in which the securities are traded. Level 2 items include cash and equivalents and fixed income securities. Cash and equivalents include money market fund investments and cash collateral supporting derivative financial instruments. Fixed income securities include corporate and government bonds, which are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings. Certain investments that are measured at fair value using the net asset value practical expedient have not been classified in the fair value hierarchy. These fair value amounts are included below to reconcile the fair value hierarchy to the respective total plan assets.


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At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions):


	2023				2022
	Fair	Level	Level	Level	Fair	Level	Level	Level
Alliant Energy	Value	1	2	3	Value	1	2	3
Cash and equivalents	$19	$—	$19	$—	$79	$—	$79	$—
Equity securities	223	223	—	—	185	185	—	—

Global asset securities	39	39	—	—	35	35	—	—
Fixed income securities	143	31	112	—	130	30	100	—
Total assets in fair value hierarchy	424	$293	$131	$—	429	$250	$179	$—
Assets measured at net asset value	306				276
Accrued investment income	2				1

Total pension plan assets	$732				$706


	2023				2022
	Fair	Level	Level	Level	Fair	Level	Level	Level
IPL	Value	1	2	3	Value	1	2	3
Cash and equivalents	$9	$—	$9	$—	$62	$—	$62	$—
Equity securities	107	107	—	—	83	83	—	—

Global asset securities	19	19	—	—	16	16	—	—
Fixed income securities	69	15	54	—	58	13	45	—
Total assets in fair value hierarchy	204	$141	$63	$—	219	$112	$107	$—
Assets measured at net asset value	147				124
Accrued investment income	1				1

Total pension plan assets	$352				$344


	2023				2022
	Fair	Level	Level	Level	Fair	Level	Level	Level
WPL	Value	1	2	3	Value	1	2	3
Cash and equivalents	$8	$—	$8	$—	$13	$—	$13	$—
Equity securities	93	93	—	—	82	82	—	—

Global asset securities	16	16	—	—	16	16	—	—
Fixed income securities	60	13	47	—	57	13	44	—
Total assets in fair value hierarchy	177	$122	$55	$—	168	$111	$57	$—
Assets measured at net asset value	128				122
Accrued investment income	1				1

Total pension plan assets	$306				$291

At December 31, the fair values of OPEB plan assets were as follows (in millions):


	2023				2022
	Fair	Level	Level	Level	Fair	Level	Level	Level
Alliant Energy	Value	1	2	3	Value	1	2	3
Cash and equivalents	$9	$—	$9	$—	$3	$—	$3	$—
Equity securities	8	8	—	—	9	9	—	—

Global asset securities	—	—	—	—	1	1	—	—
Fixed income securities	47	47	—	—	47	46	1	—
Total assets in fair value hierarchy	64	$55	$9	$—	60	$56	$4	$—
Assets measured at net asset value	19				23


Total OPEB plan assets	$83				$83


	2023				2022
	Fair	Level	Level	Level	Fair	Level	Level	Level
IPL	Value	1	2	3	Value	1	2	3
Cash and equivalents	$1	$—	$1	$—	$1	$—	$1	$—
Equity securities	6	6	—	—	5	5	—	—


Fixed income securities	36	36	—	—	34	34	—	—
Total assets in fair value hierarchy	43	$42	$1	$—	40	$39	$1	$—
Assets measured at net asset value	18				18


Total OPEB plan assets	$61				$58


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	2023				2022
	Fair	Level	Level	Level	Fair	Level	Level	Level
WPL	Value	1	2	3	Value	1	2	3
Cash and equivalents	$1	$—	$1	$—	$—	$—	$—	$—
Equity securities	2	2	—	—	1	1	—	—
Fixed income securities	11	11	—	—	13	13	—	—
Total OPEB plan assets	$14	$13	$1	$—	$14	$14	$—	$—

For the various defined benefit pension and OPEB plans, Alliant Energy common stock represented less than 1% of assets directly held in the plans at December 31, 2023 and 2022.

401(k) Savings Plans - A significant number of employees participate in defined contribution retirement plans (401(k) savings plans). Alliant Energy common stock directly held by participants represented 8% and 10% of total assets in the 401(k) savings plans at December 31, 2023 and 2022, respectively. Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
401(k) costs	$30	$28	$26	$14	$13	$13	$14	$13	$12

NOTE 13(b) Equity-based Compensation Plans - In 2020, Alliant Energy’s shareowners approved the 2020 OIP, which permits the grant of shares of Alliant Energy common stock, restricted stock, restricted stock units, performance shares, performance units, and other stock-based or cash-based awards to key employees. At December 31, 2023, performance shares and restricted stock units (performance- and time-vesting) were outstanding under the 2020 OIP, and 8 million shares of Alliant Energy common stock remained available for grants under the 2020 OIP. Alliant Energy satisfies share payouts related to equity awards through the issuance of new shares of its common stock. Nonvested awards generally do not have non-forfeitable rights to dividends or dividend equivalents when dividends are paid to common shareowners. A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards was as follows (in millions):


	Alliant Energy			IPL			WPL
	2023	2022	2021	2023	2022	2021	2023	2022	2021
Compensation expense	$12	$13	$14	$6	$7	$8	$5	$5	$6
Income tax benefits	3	3	4	2	2	2	1	1	2

As of December 31, 2023, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $8 million, $4 million and $3 million, respectively, which is expected to be recognized over a weighted average period of between one year and two years. Share-based compensation expense is recognized on a straight-line basis over the requisite service periods and is recorded in “Other operation and maintenance” in the income statements. As of December 31, 2023, 429,804 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

Performance Shares - Equity Awards - Payouts of performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group. Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these performance shares is based on the fair value of the underlying common stock on the grant date and the probability of satisfying the market condition contained in the agreement during a three-year performance period. The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of shares. If minimum performance targets are not met during the performance period, these performance shares are forfeited. Compensation expense is recorded ratably over the performance period based on the fair value of the awards at the grant date. A summary of the performance shares activity, with amounts representing the target number of awards, was as follows:


	2023		2022		2021
	Shares	Weighted Average Grant Date Fair Value	Shares	Weighted Average Grant Date Fair Value	Shares	Weighted Average Grant Date Fair Value
Nonvested awards, January 1	190,273	$54.13	196,429	$51.59	129,156	$54.63
Granted	108,712	55.68	74,106	54.45	73,112	46.19
Vested	(53,431)	64.04	(71,101)	47.48	—	—
Forfeited	(11,600)	53.88	(9,161)	53.99	(5,839)	51.07
Nonvested awards, December 31	233,954	52.60	190,273	54.13	196,429	51.59


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Restricted Stock Units - Equity Awards - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period. Restricted stock unit grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards. The fair value of each of these restricted stock units is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on the fair value of the awards on the grant date. A summary of the restricted stock units activity was as follows:


	2023		2022		2021
	Units	Weighted Average Grant Date Fair Value	Units	Weighted Average Grant Date Fair Value	Units	Weighted Average Grant Date Fair Value
Nonvested units, January 1	198,275	$54.53	217,819	$50.54	146,549	$51.54
Granted	106,124	52.77	77,122	56.88	80,152	48.65
Vested	(55,345)	59.40	(82,770)	46.08	—	—
Forfeited	(14,795)	54.53	(13,896)	55.53	(8,882)	49.84
Nonvested units, December 31	234,259	52.58	198,275	54.53	217,819	50.54

Performance Restricted Stock Units - Equity Awards - Payouts of performance restricted stock units are based upon achievement of certain performance targets during a three-year performance period, which currently includes specified growth of consolidated net income from continuing operations, as well as a diversity metric for the 2022 and 2023 grants. The actual number of units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200% of the target number of units under each award type. If minimum performance targets are not met during the performance period, these units are forfeited. Performance restricted stock units are to be paid out in shares and are accounted for as equity awards. The fair value of each performance restricted stock unit is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award. Compensation expense is recorded ratably over the performance period based on a probability assessment of payouts for the awards at each reporting period. A summary of the performance restricted stock units activity, with amounts representing the target number of units, was as follows:


	2023		2022		2021
	Units	Weighted Average Grant Date Fair Value	Units	Weighted Average Grant Date Fair Value	Units	Weighted Average Grant Date Fair Value
Nonvested units, January 1	199,874	$54.74	196,429	$50.74	197,463	$47.31
Granted	124,217	52.71	84,670	57.01	73,112	48.66
Vested	(53,431)	59.36	(71,101)	46.24	(68,307)	38.60
Forfeited	(13,021)	55.47	(10,124)	55.92	(5,839)	50.46
Nonvested units, December 31	257,639	52.76	199,874	54.74	196,429	50.74

NOTE 13(c) Deferred Compensation Plan - Alliant Energy maintains a DCP under which certain key employees may defer up to 100% of base salary and short-term cash incentive compensation and members of its Board of Directors may elect to defer all or part of their retainer and committee fees. Key employees who have made the maximum allowed contribution to the Alliant Energy 401(k) Savings Plan may receive an additional credit to the DCP. Key employees and Board of Directors members may elect to have their deferrals credited to a company stock account, an interest account, equity accounts or mutual fund accounts based on certain benchmark funds.

Company Stock Account - The DCP does not permit diversification of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock. The deferred compensation obligations for participants’ company stock accounts are recorded in “Additional paid-in capital” and the shares of Alliant Energy common stock held in a rabbi trust to satisfy this obligation are recorded in “Shares in deferred compensation trust” on Alliant Energy’s balance sheets. At December 31, the carrying value of the deferred compensation obligation for the company stock account and the shares in the deferred compensation trust based on the historical value of the shares of Alliant Energy common stock contributed to the rabbi trust, and the fair market value of the shares held in the rabbi trust, were as follows (in millions):


	2023	2022
Carrying value	$13	$13
Fair market value	19	22

Interest, Equity and Mutual Fund Accounts - Distributions from participants’ interest, equity and mutual fund accounts are in the form of cash payments. The deferred compensation obligations for participants’ interest, equity and mutual fund accounts are recorded in “Pension and other benefit obligations” on the balance sheets. At December 31, 2023 and 2022, the carrying value of Alliant Energy’s deferred compensation obligations for participants’ interest, equity and mutual fund accounts, which approximates fair market value, was $21 million and $19 million, respectively.


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NOTE 14. ASSET RETIREMENT OBLIGATIONS

Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, wind farms, active ash landfills, ash ponds, solar generation, above ground storage tanks and batteries. Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls. AROs are recorded in “Other current liabilities” and “Other liabilities” on the balance sheets. Refer to Note 2 for information regarding regulatory assets related to AROs. A reconciliation of the changes in AROs associated with long-lived assets is as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Balance, January 1	$279	$294	$195	$213	$84	$81
Revisions in estimated cash flows	(6)	19	(9)	15	3	4
Liabilities settled	(51)	(48)	(44)	(39)	(7)	(9)
Liabilities incurred	16	6	1	—	15	6
Accretion expense	8	8	5	6	3	2
Balance, December 31	$246	$279	$148	$195	$98	$84

NOTE 15. DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Purpose - Derivative instruments were utilized for risk management purposes to mitigate pricing volatility for fuel used to supply natural gas-fired EGUs, natural gas supplied to retail customers, and purchased electricity, as well as optimize the value of natural gas pipeline capacity and electric generation, which may include swap, physical forward and option contracts. In addition, FTRs help manage transmission congestion costs in the MISO market. Risk policies are maintained that govern the use of such derivative instruments.

Notional Amounts - As of December 31, 2023, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):


	Electricity		FTRs		Natural Gas
	MWhs	Years	MWhs	Years	Dths	Years
Alliant Energy	1,640	2024-2026	11,927	2024	176,349	2024-2032
IPL	673	2024-2026	5,336	2024	74,360	2024-2030
WPL	967	2024-2026	6,591	2024	101,989	2024-2032

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheet as assets or liabilities. At December 31, the fair values of current derivative assets are included in “Other current assets,” non-current derivative assets are included in “Deferred charges and other,” current derivative liabilities are included in “Other current liabilities” and non-current derivative liabilities are included in “Other liabilities” on the balance sheets as follows (in millions):


	Alliant Energy		IPL		WPL
	2023	2022	2023	2022	2023	2022
Current derivative assets	$44	$111	$30	$69	$14	$42
Non-current derivative assets	44	126	24	69	20	57
Current derivative liabilities	51	59	22	40	29	19
Non-current derivative liabilities	47	20	8	6	39	14

In 2023, Alliant Energy’s, IPL’s and WPL’s derivative assets decreased primarily due to settlements of natural gas and electricity contracts, and lower natural gas prices. Alliant Energy’s, IPL’s and WPL’s non-current derivative liabilities increased primarily due to lower natural gas prices. Alliant Energy’s and IPL’s current derivative liabilities decreased primarily due to settlements of natural gas contracts. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets.

Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At December 31, 2023 and 2022, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.


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Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets at December 31 as follows:


	Alliant Energy		IPL		WPL
	Gross		Gross		Gross
	(as reported)	Net	(as reported)	Net	(as reported)	Net
2023
Derivative assets	$88	$47	$54	$32	$34	$15
Derivative liabilities	98	57	30	8	68	49
2022
Derivative assets	237	193	138	108	99	85
Derivative liabilities	79	35	46	16	33	19

Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

Interest Rate Derivative - In January 2023, AEF entered into a $300 million interest rate swap maturing in January 2026 to mitigate interest rate risk. Under the terms of the swap, AEF exchanged a variable interest rate for a fixed interest rate of 3.93% on a portion of its variable-rate term loan borrowings. The related interest rate derivative was valued based on quoted prices that utilize current market interest rate forecasts. As of December 31, 2023, $1 million of non-current interest rate derivative assets was recorded in “Deferred charges and other” on Alliant Energy’s balance sheet. This interest rate derivative was designated as a cash flow hedge, with changes in fair value recorded as other comprehensive income/loss. As of December 31, 2023, accumulated other comprehensive income included $1 million of income related to the interest rate swap. In 2023, $3 million of reductions to interest expense were recorded in Alliant Energy’s income statement related to the interest rate swap.

NOTE 16. FAIR VALUE MEASUREMENTS

Valuation Hierarchy - Fair value measurement accounting establishes three levels of fair value hierarchy that prioritize the inputs to valuation techniques used to measure fair value. Level 1 pricing inputs are quoted prices available in active markets for identical assets or liabilities as of the reporting date. Level 2 pricing inputs are quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in markets that are not active as of the reporting date. Level 3 pricing inputs are unobservable inputs for assets or liabilities for which little or no market data exist and require significant management judgment or estimation.

The fair value hierarchy gives the highest priority to quoted prices in active markets (Level 1) and the lowest priority to unobservable data (Level 3). In some cases, the inputs used to measure fair value might fall in different levels of the fair value hierarchy. The lowest level input that is significant to a fair value measurement in its entirety determines the applicable level in the fair value hierarchy. Assessing the significance of a particular input to the fair value measurement in its entirety requires judgment, considering factors specific to the asset or liability.

Valuation Techniques -

Derivative assets and derivative liabilities - Swap, option and physical forward commodity contracts were non-exchange-based derivative instruments and were valued using indicative price quotations from a pricing vendor that provides daily exchange forward price settlements, from broker or dealer quotations, from market publications or from on-line exchanges. The indicative price quotations reflected the average of the bid-ask mid-point prices and were obtained from sources believed to provide the most liquid market for the commodity. A portion of these indicative price quotations were corroborated using quoted prices for similar assets or liabilities in active markets and categorized derivative instruments based on such indicative price quotations as Level 2. Commodity contracts that were valued using indicative price quotations based on significant assumptions such as seasonal or monthly shaping and indicative price quotations that could not be readily corroborated were categorized as Level 3. Swap, option and physical forward commodity contracts were predominately at liquid trading points. FTRs were valued using auction prices and were categorized as Level 3. Refer to Note 15 for additional details of derivative assets and derivative liabilities.

Deferred proceeds (sales of receivables) - The fair value of IPL’s deferred proceeds related to its sales of accounts receivable program was calculated each reporting date using the cost approach valuation technique. The fair value represents the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold due to the short-term nature of the collection period. These inputs were considered unobservable and deferred proceeds were categorized as Level 3. Deferred proceeds represent IPL’s maximum exposure to loss related to the receivables sold. Refer to Note 5(b) for additional information regarding deferred proceeds.


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Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on a discounted cash flow methodology using observable data from comparably traded securities with similar credit profiles, and was substantially classified as Level 2. Refer to Note 9(b) for additional information regarding long-term debt.

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):


Alliant Energy	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	88	—	59	29	88	237	—	206	31	237
Interest rate derivatives	1	—	1	—	1	—	—	—	—	—
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	98	—	93	5	98	79	—	67	12	79

Long-term debt (incl. current maturities)	9,034	—	8,677	—	8,677	8,076	—	7,338	1	7,339


IPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Money market fund investments	$45	$45	$—	$—	$45	$10	$10	$—	$—	$10
Commodity derivatives	54	—	30	24	54	138	—	111	27	138
Deferred proceeds	216	—	—	216	216	185	—	—	185	185
Liabilities and equity:
Commodity derivatives	30	—	25	5	30	46	—	35	11	46
Long-term debt (incl. current maturities)	3,945	—	3,664	—	3,664	3,646	—	3,228	—	3,228


WPL	2023					2022
		Fair Value					Fair Value
	Carrying	Level	Level	Level		Carrying	Level	Level	Level
	Amount	1	2	3	Total	Amount	1	2	3	Total
Assets:
Commodity derivatives	$34	$—	$29	$5	$34	$99	$—	$95	$4	$99
Liabilities and equity:
Commodity derivatives	68	—	68	—	68	33	—	32	1	33
Long-term debt	3,070	—	2,933	—	2,933	2,770	—	2,542	—	2,542

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):


Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$19	$29	$185	$214
Total net gains (losses) included in changes in net assets (realized/unrealized)	3	(18)	—	—


Purchases	62	79	—	—
Sales	(3)	(2)	—	—
Settlements (a)	(57)	(69)	31	(29)
Ending balance, December 31	$24	$19	$216	$185
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$3	($18)	$—	$—


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IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
	2023	2022	2023	2022
Beginning balance, January 1	$16	$18	$185	$214
Total net losses included in changes in net assets (realized/unrealized)	(3)	(12)	—	—


Purchases	51	58	—	—
Sales	(3)	(1)	—	—
Settlements (a)	(42)	(47)	31	(29)
Ending balance, December 31	$19	$16	$216	$185
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at December 31	($3)	($13)	$—	$—


WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
	2023	2022
Beginning balance, January 1	$3	$11
Total net gains (losses) included in changes in net assets (realized/unrealized)	6	(6)


Purchases	11	21
Sales	—	(1)
Settlements (a)	(15)	(22)
Ending balance, December 31	$5	$3
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31	$6	($5)

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) at December 31 as follows (in millions):


	Alliant Energy		IPL		WPL
	Excluding FTRs	FTRs	Excluding FTRs	FTRs	Excluding FTRs	FTRs
2023	$3	$21	$3	$16	$—	$5
2022	(10)	29	(9)	25	(1)	4

NOTE 17. COMMITMENTS AND CONTINGENCIES

NOTE 17(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including IPL’s and WPL’s expansion of solar generation, WPL’s expansion of battery storage, and IPL’s repowering of the existing Franklin County wind farm. At December 31, 2023, Alliant Energy’s, IPL’s, and WPL’s minimum future commitments in 2024 for these projects were $188 million, $131 million, and $57 million, respectively.

NOTE 17(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At December 31, 2023, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):


Alliant Energy	2024	2025	2026	2027	2028	Thereafter	Total

Natural gas	$301	$187	$123	$78	$49	$142	$880
Coal	94	49	8	8	6	—	165
Other (a)	61	17	14	9	2	22	125
	$456	$253	$145	$95	$57	$164	$1,170


IPL	2024	2025	2026	2027	2028	Thereafter	Total

Natural gas	$165	$86	$47	$35	$14	$25	$372
Coal	49	35	8	8	6	—	106
Other (a)	23	2	2	2	2	22	53
	$237	$123	$57	$45	$22	$47	$531


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WPL	2024	2025	2026	2027	2028	Thereafter	Total

Natural gas	$136	$101	$76	$43	$35	$117	$508
Coal	45	14	—	—	—	—	59
Other (a)	23	1	1	—	—	—	25
	$204	$116	$77	$43	$35	$117	$592

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at December 31, 2023.

NOTE 17(c) Legal Proceedings - Alliant Energy, IPL and WPL are involved in legal and administrative proceedings before various courts and agencies with respect to matters arising in the ordinary course of business. Although unable to predict the outcome of these matters, Alliant Energy, IPL and WPL believe that appropriate reserves have been established and final disposition of these actions will not have a material effect on their financial condition or results of operations.

NOTE 17(d) Guarantees and Indemnifications -

Whiting Petroleum - Whiting Petroleum is an independent oil and gas company. In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations.

As of December 31, 2023, the currently known partnership obligations for the abandonment obligations are estimated at $49 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy estimates its expected loss to be a portion of the $49 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners. Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of December 31, 2023 and 2022.

Whiting Petroleum completed a business combination with Oasis Petroleum Inc. in 2022. The combined operations are now known as Chord Energy Corporation. The business combination is not expected to affect the scope of the Whiting Petroleum affiliate’s obligations to Alliant Energy or Alliant Energy’s related guarantees.

Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third-party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $51 million as of December 31, 2023 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of December 31, 2023 and 2022.

Transfers of Renewable Tax Credits - In 2023, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and battery storage facilities to other corporate taxpayers in exchange for cash. IPL and WPL provided indemnifications associated with $76 million and $22 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers in 2023 in the event of an adverse interpretation of tax law, including whether the related tax credits meet the qualification requirements. Alliant Energy, IPL and WPL believe the likelihood of having to make any material cash payments under these indemnifications is remote.

NOTE 17(e) Environmental Matters - Alliant Energy, IPL and WPL are subject to environmental regulations as a result of their current and past operations. These regulations are designed to protect public health and the environment and have resulted in compliance, remediation, containment and monitoring obligations, which are recorded as current and non-current environmental liabilities. Substantially all of the environmental liabilities recorded on the balance sheets relate to MGP sites.

Manufactured Gas Plant Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At December 31, 2023, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the


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MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):


	Alliant Energy			IPL			WPL
Range of estimated future costs	$9	-	$36	$5	-	$11	$4	-	$25
Current and non-current environmental liabilities	$18			$8			$10

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential CAA issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.

Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: CSAPR, Effluent Limitation Guidelines, CCR Rule, and various legislation and EPA regulations to monitor and regulate the emission of GHG, including the CAA.

NOTE 17(f) Credit Risk - IPL provides retail electric and gas services in Iowa and wholesale electric service in Minnesota, Illinois and Iowa. WPL provides retail electric and gas services and wholesale electric service in Wisconsin. The geographic concentration of IPL’s and WPL’s customers did not contribute significantly to overall credit risk exposure. In addition, as a result of a diverse customer base, IPL and WPL did not have any significant credit risk concentration for receivables arising from the sale of electricity or gas services.

Alliant Energy, IPL and WPL are subject to credit risk related to the ability of counterparties to meet their contractual payment obligations or the potential non-performance of counterparties to deliver contracted commodities and other goods or services at the contracted price. Credit policies are maintained to mitigate credit risk. These credit policies include evaluation of the financial condition of certain counterparties, use of credit risk-related contingent provisions in certain agreements that require credit support from counterparties not meeting specific criteria, diversification of counterparties to reduce concentrations of credit risk and the use of standardized agreements that facilitate the netting of cash flows associated with certain counterparties. Based on these credit policies and counterparty diversification, as well as utility cost recovery mechanisms, it is unlikely that counterparty non-performance would have a material effect on financial condition or results of operations. However, there is no assurance that these items will protect against all losses from counterparty non-performance.

Refer to Notes 5(a) and 15 for details of allowances for expected credit losses and credit risk-related contingent features, respectively.

NOTE 17(g) MISO Transmission Owner Return on Equity Complaints - A group of stakeholders, including MISO cooperative and municipal utilities, previously filed complaints with FERC requesting a reduction to the base return on equity authorized for MISO transmission owners, including ITC and ATC. In 2019, FERC issued an order on the previously filed complaints and reduced the base return on equity authorized for the MISO transmission owners to 9.88% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2020, FERC issued orders in response to various rehearing requests and increased the base return on equity authorized for the MISO transmission owners from 9.88% to 10.02% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2022, the U.S. Court of Appeals for the District of Columbia vacated FERC’s prior orders that established the base return on equity authorized for the MISO transmission owners and remanded the cases to FERC for further proceedings, which may result in additional changes to the base return on equity authorized for the MISO transmission owners. As a result of the 2022 court decision, Alliant Energy recorded a $6 million reduction in “Equity income from unconsolidated investments” in its income statement in 2022 to reflect the anticipated reduction in the base return on equity authorized for the MISO transmission owners. Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs.

NOTE 17(h) Collective Bargaining Agreements - At December 31, 2023, employees covered by collective bargaining agreements represented 53%, 69% and 83% of total employees of Alliant Energy, IPL and WPL, respectively. In August 2024, IPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 204 (Cedar Rapids) expires, representing 18% and 53% of total employees of Alliant Energy and IPL, respectively.


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NOTE 18. SEGMENTS OF BUSINESS

Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2023 are:

Utility -** includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin. The utility business has three reportable segments: a) utility electric operations; b) utility gas operations; and c) utility other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.”
ATC Holdings, Non-utility, Parent and Other -** includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments. AEF is comprised of Alliant Energy’s interest in ATC Holdings, Travero, a non-utility wind farm, corporate venture investments, the Sheboygan Falls Energy Facility and other non-utility holdings.

Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable. In all other cases, administrative support services are allocated to the applicable segment based on services agreements. Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues. All of Alliant Energy’s operations and assets are located in the U.S. Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):


					ATC Holdings,
	Utility				Non-utility,	Alliant Energy
2023	Electric	Gas	Other	Total	Parent and Other	Consolidated
Revenues	$3,345	$540	$52	$3,937	$90	$4,027
Depreciation and amortization	602	60	6	668	8	676
Operating income	827	70	19	916	27	943
Interest expense				304	90	394
Equity income from unconsolidated investments, net	(3)	—	—	(3)	(58)	(61)
Income taxes				2	2	4
Net income (loss) attributable to Alliant Energy common shareowners				711	(8)	703
Total assets	17,833	1,684	606	20,123	1,114	21,237
Investments in equity method subsidiaries	21	—	—	21	564	585
Construction and acquisition expenditures	1,641	90	—	1,731	123	1,854


					ATC Holdings,
	Utility				Non-utility,	Alliant Energy
2022	Electric	Gas	Other	Total	Parent and Other	Consolidated
Revenues	$3,421	$642	$49	$4,112	$93	$4,205
Depreciation and amortization	601	56	7	664	7	671
Operating income	805	97	3	905	23	928
Interest expense				269	56	325
Equity income from unconsolidated investments, net	(1)	—	—	(1)	(50)	(51)
Income taxes				16	6	22
Net income attributable to Alliant Energy common shareowners				675	11	686
Total assets	16,571	1,631	860	19,062	1,101	20,163
Investments in equity method subsidiaries	20	—	—	20	522	542
Construction and acquisition expenditures	1,318	74	—	1,392	92	1,484


					ATC Holdings,
	Utility				Non-utility,	Alliant Energy
2021	Electric	Gas	Other	Total	Parent and Other	Consolidated
Revenues	$3,081	$456	$49	$3,586	$83	$3,669
Depreciation and amortization	591	54	6	651	6	657
Operating income (loss)	716	63	(11)	768	27	795
Interest expense				244	33	277
Equity income from unconsolidated investments, net	(2)	—	—	(2)	(60)	(62)
Income tax expense (benefit)				(87)	13	(74)
Net income attributable to Alliant Energy common shareowners				618	41	659
Total assets	14,924	1,487	1,103	17,514	1,039	18,553
Investments in equity method subsidiaries	17	—	—	17	491	508
Construction and acquisition expenditures	980	90	—	1,070	99	1,169


			97

Table of C o ntents

IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes steam operations and the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues. All of IPL’s operations and assets are located in the U.S. Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):


2023	Electric	Gas	Other	Total
Revenues	$1,761	$300	$49	$2,110
Depreciation and amortization	348	34	6	388
Operating income	390	35	19	444
Interest expense				155
Income tax benefit				(58)
Net income available for common stock				366
Total assets	9,311	921	257	10,489
Construction and acquisition expenditures	671	41	—	712


2022	Electric	Gas	Other	Total
Revenues	$1,859	$351	$46	$2,256
Depreciation and amortization	342	32	7	381
Operating income	397	53	3	453
Interest expense				148
Income tax benefit				(50)
Net income available for common stock				360
Total assets	8,686	872	517	10,075
Construction and acquisition expenditures	336	36	—	372


2021	Electric	Gas	Other	Total
Revenues	$1,752	$265	$46	$2,063
Depreciation and amortization	338	31	6	375
Operating income (loss)	420	43	(3)	460
Interest expense				139
Income tax benefit				(36)
Net income available for common stock				350
Total assets	8,602	819	575	9,996
Construction and acquisition expenditures	342	42	—	384

WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments: a) electric operations; b) gas operations; and c) other, which includes the unallocated portions of the utility business. Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues. All of WPL’s operations and assets are located in the U.S. Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):


2023	Electric	Gas	Other	Total
Revenues	$1,584	$240	$3	$1,827
Depreciation and amortization	254	26	—	280
Operating income	437	35	—	472
Interest expense				149

Income taxes				60
Net income				345
Total assets	8,522	763	349	9,634

Construction and acquisition expenditures	970	49	—	1,019


			98

Table of C o ntents


2022	Electric	Gas	Other	Total
Revenues	$1,562	$291	$3	$1,856
Depreciation and amortization	259	24	—	283
Operating income	408	44	—	452
Interest expense				121

Income taxes				66
Net income				315
Total assets	7,885	759	343	8,987

Construction and acquisition expenditures	982	38	—	1,020


2021	Electric	Gas	Other	Total
Revenues	$1,329	$191	$3	$1,523
Depreciation and amortization	253	23	—	276
Operating income (loss)	296	20	(8)	308
Interest expense				105

Income tax benefit				(51)
Net income				268
Total assets	6,322	668	528	7,518

Construction and acquisition expenditures	638	48	—	686

NOTE 19. RELATED PARTIES

Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases were as follows (in millions):


	IPL			WPL
	2023	2022	2021	2023	2022	2021
Corporate Services billings	$181	$181	$180	$163	$155	$154
Sales credited	11	19	22	55	74	23
Purchases billed	431	435	441	35	174	116

As of December 31, net intercompany payables to Corporate Services were as follows (in millions):


	2023	2022
IPL	$129	$103
WPL	72	56

ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties were as follows (in millions):


	2023	2022	2021
ATC billings to WPL	$159	$140	$122
WPL billings to ATC	20	18	18

As of December 31, 2023 and 2022, WPL owed ATC net amounts of $10 million and $10 million, respectively.

WPL’s Sheboygan Falls Energy Facility Lease - Refer to Note 10 for discussion of WPL’s Sheboygan Falls Energy Facility lease.

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