Cover and table of contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2025

or

Commission file number: 000-51026

Monolithic Power Systems, Inc.

(Exact name of registrant as specified in its charter)

(561) 839-3999

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☒ No ☐

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ☐ No ☒

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☒

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b). ☒

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). ☐ Yes ☒ No

The aggregate market value of the voting and non-voting common equity held by non-affiliates of the registrant, based upon the closing price of the common stock on the Nasdaq Global Select Market on June 30, 2025, was $ 24.7 billion (2).

There were 49,118,000 shares of the registrant’s common stock issued and outstanding as of February 20, 2026.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s Proxy Statement for the 2026 Annual Meeting of Stockholders are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. The Proxy Statement will be filed with the Securities and Exchange Commission within 120 days of the registrant’s fiscal year ended December 31, 2025.

Explanatory Note

Restatement of Previously Issued Consolidated Financial Statements

On February 26, 2026, the Audit Committee of the Board of Directors of Monolithic Power Systems, Inc. (the “Company”), after discussion with senior management and the Company’s independent registered public accountants, determined that the Company’s previously issued audited consolidated financial statements included in its annual report on Form 10-K for the fiscal year ended December 31, 2024, filed on March 3, 2025, and each of the Company’s previously issued unaudited condensed consolidated financial statements included in its quarterly reports on Form 10-Q for each of the quarterly periods in 2025 (each a “Previous Filing” and collectively “Previous Filings”), should no longer be relied upon due to the impact of an unintentional error.

The required restatement was discovered in connection with the preparation of this Annual Report on Form 10-K for the fiscal year ended December 31, 2025. The Company engaged third-party tax service providers in connection with the original determination of the accounting for deferred income taxes associated with a one-time tax incentive granted by a certain foreign jurisdiction. Nevertheless, the Company concluded that in the prior year it had not appropriately accounted for the deferred income taxes associated with the tax incentive. The restatement results in a decrease to income tax benefit, net and net deferred income taxes by $194.6 million in the consolidated financial statements as of and for the year ended December 31, 2024.

This Annual Report on Form 10-K includes restated Consolidated Financial Statements as of and for the years ended December 31, 2024. In addition, the Company has restated its unaudited quarterly Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Operations, Condensed Consolidated Statements of Comprehensive Income, and Condensed Consolidated Statements of Stockholders’ Equity for each of the quarters in the year ended December 31, 2025.

Comparative amounts in 2025 presented in the Company’s Quarterly Reports on Form 10-Q for the periods ending March 31, 2026, June 30, 2026 and September 30, 2026 will be changed retrospectively to reflect the restatement. Accordingly, investors should rely only on the financial information and other disclosures regarding the restated periods in this Form 10-K or in future filings with the Securities and Exchange Commission (as applicable), and not on any Previous Filings, earnings releases or similar communications relating to the restated periods.

Refer to Note 2, Restatement of Previously Issued Consolidated Financial Statements and Note 17, Restatement of Previously Issued Condensed Consolidated Financial Statements (unaudited) in the accompanying Consolidated Financial Statements included in Part II, Item 8 for additional information, including the impact on the specific accounts.

Items Restated in this Form 10-K