UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

Commission file number: 1-7933

Aon plc

(Exact name of registrant as specified in its charter)

Metropolitan Building, James Joyce Street, Dublin 1, Ireland D01 K0Y8

(Address of principal executive offices) (Zip Code)

+353 1 266 6000

(Registrant’s Telephone Number, including area code) Securities registered pursuant to Section 12(b) of the Act:

S****ecurities 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 Exchange 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. ☒

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

As of June 30, 2020, the aggregate market value of the registrant’s Class A Ordinary Shares held by non-affiliates of the registrant was $44,593,079,186 based on the closing sales price as reported on the New York Stock Exchange — Composite Transaction Listing.

Number of the registrant’s Class A Ordinary Shares of Aon plc, $0.01 nominal value, outstanding as of February 18, 2021: 225,984,346.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s proxy statement for its 2021 Annual General Meeting of Shareholders are incorporated by reference in this report in response to Part III, Items 10, 11, 12, 13, and 14.

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

Information Concerning Forward-Looking Statements

This report contains certain statements related to future results, or states our intentions, beliefs, and expectations or predictions for the future, which are forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. Forward-looking statements represent management’s expectations or forecasts of future events. Forward-looking statements are typically identified by words such as “anticipate,” “believe,” “estimate,” “expect,” “forecast,” “project,” “intend,” “plan,” “probably,” “potential,” “looking forward,” “continue,” and other similar terms, and future or conditional tense verbs like “could,” “may,” “might,” “should,” “will,” and “would.” You can also identify forward-looking statements by the fact that they do not relate strictly to historical or current facts. For example, we may use forward-looking statements when addressing topics such as: market and industry conditions, including competitive and pricing trends; changes in our business strategies and methods of generating revenue; the development and performance of our services and products; changes in the composition or level of our revenues; our cost structure and the outcome of cost-saving or restructuring initiatives; the outcome of contingencies; dividend policy; the expected impact of acquisitions, dispositions, and other significant transactions, such as the Combination, as defined in Part I, Item 1 of this report; pension obligations; cash flow and liquidity; expected effective tax rate; future actions by regulators; and the impact of changes in accounting rules. These forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from either historical or anticipated results depending on a variety of factors. Potential factors, which may be revised or supplemented in subsequent reports filed or furnished with the Securities and Exchange Commission (the “SEC”), that could impact results include:

• changes in the competitive environment or damage to our reputation;

• fluctuations in currency exchange and interest rates that could impact our financial condition or results;

• changes in global equity and fixed income markets that could affect the return on invested assets;

• changes in the funded status of our various defined benefit pension plans and the impact of any increased pension funding resulting from those changes;

• the level of our debt and the terms thereof reducing our flexibility or increasing borrowing costs;

• rating agency actions that could limit our access to capital and our competitive position ;

• our global tax rate being subject to a variety of different factors, which could create volatility in that tax rate;

• changes in our accounting estimates and assumptions on our financial statements;

• limits on our subsidiaries’ ability to pay dividends or otherwise make payments to us;

• the impact of legal proceedings and other contingencies, including those arising from errors and omissions and other claims against us;

• the impact of, and potential challenges in complying with, laws and regulations of the jurisdictions in which we operate, particularly given the global nature of operations and the possibility of differing or conflicting laws and regulations, or the application or interpretation thereof, across such jurisdictions;

• the impact of any regulatory investigations brought in Ireland, the United Kingdom (the “U.K.”), the United States (the “U.S”). and other countries;

• failure to protect intellectual property rights or allegations that we have infringed on the intellectual property rights of others;

• general economic and political conditions in the countries in which we do business around the world, including the withdrawal of the U.K. from the European Union (the “E.U.”)

• the failure to retain, attract and develop experienced and qualified personnel;

• international risks associated with our global operations;

• the effects of natural or man-made disasters, including the effects of the COVID-19 and other health pandemics;

• the potential for a system or network disruption or breach to result in operational interruption or improper disclosure of confidential, personal, or proprietary data;

• our ability to develop and implement new technology;

• damage to our reputation among clients, colleagues, markets or third parties;

• the actions taken by third parties that perform aspects of our business operations and client services;

• the extent to which we are exposed to certain risks, including lawsuits, related to our actions we may take in acting in a being responsible for making decisions on behalf of clients in our investment consulting business or in other advisory services that we currently provide, or will provide in the future;

• our ability to continue, and the costs and risks associated with, growing, developing and integrating acquired business, and entering into new lines of business or products;

• changes in commercial property and casualty markets, commercial premium rates or methods of compensation;

• our ability to implement initiatives intended to yield cost savings and the ability to achieve those cost savings;

• the effects of Irish law on our operating flexibility and the enforcement of judgments against us; and

• risks and uncertainties associated with the Combination, including our ability to obtain the requisite approvals of, to satisfy the other conditions to, or to otherwise complete, the Combination on the expected time frame, or at all, the occurrence of unanticipated difficulties or costs in connection with the Combination, our ability to successfully integrate the combined companies following the Combination and our ability to realize the expected benefits from the Combination.

Any or all of our forward-looking statements may turn out to be inaccurate, and there are no guarantees about our performance. The factors identified above are not exhaustive. Aon and its subsidiaries operate in a dynamic business environment in which new risks may emerge frequently. Accordingly, readers should not place undue reliance on forward-looking statements, which speak only as of the dates on which they are made. We are under no (and expressly disclaim any) obligation to update or alter any forward-looking statement that we may make from time to time, whether as a result of new information, future events, or otherwise. Further information about factors that could materially affect Aon, including our results of operations and financial condition, is contained in the “Risk Factors” section in Part I, Item 1A of this report.

Table of Contents

PART I

OVERVIEW

Aon plc (which may be referred to as “Aon,” the “Company,” “we,” “us,” or “our”) is a leading global professional services firm that provides advice and solutions to clients focused on risk, retirement, and health, delivering distinctive client value via innovative and effective risk management and workforce productivity solutions that are under-pinned by industry-leading data and analytics. Our strategy is to be the preeminent professional services firm in the world, focused on risk and people.

Our clients are globally diversified and include all market segments and almost every industry in over 120 countries and sovereignties. This diversification of our customer base helps provide us stability in different economic scenarios that could affect specific industries, customer segments, or geographies.

We have continued to focus our portfolio on higher-margin, capital-light professional services businesses that have high recurring revenue streams and strong cash flow generation. We endeavor to make capital allocation decisions based upon return on invested capital.

On March 9, 2020, Aon and Willis Towers Watson Public Limited Company, an Irish public limited company (“WTW”), entered into a Business Combination Agreement with respect to a combination of the parties (the “Combination”). At the effective date of the Combination, WTW shareholders will be entitled to receive 1.08 newly issued Class A ordinary shares of Aon in exchange for each ordinary share of WTW held by such holders. Aon expects to close the Combination in the first half of 2021, subject to regulatory approval and customary closing conditions.

IRELAND REORGANIZATION

On April 1, 2020, a scheme of arrangement under English law was completed pursuant to which the Class A ordinary shares of Aon plc, a public limited company incorporated under the laws of England and Wales and the publicly traded parent company of the Aon group (“Aon Global Limited”), were cancelled and the holders thereof received, on a one-for-one basis, Class A ordinary shares of Aon plc, an Irish public limited company formerly known as Aon Limited (“Aon plc”) , as described in the proxy statement filed with the SEC on December 20, 2019 (the “Ireland Reorganization”). Aon plc is a tax resident of Ireland. References in this report to “Aon,” the “Company,” “we,” “us,” or “our” for time periods prior to April 1, 2020 refer to Aon Global Limited. References in the Financial Statements to “Aon,” the “Company,” “we,” “us,” or “our” for time periods on or after April 1, 2020, refer to Aon plc.

BUSINESS SEGMENT

The Company operates as one segment that includes all of Aon’s continuing operations, which, as a global professional services firm, provides advice and solutions to clients focused on risk, retirement, and health through five principal products and services: Commercial Risk Solutions, Reinsurance Solutions, Retirement Solutions, Health Solutions, and Data & Analytic Services. Collectively, these products and service lines make up our one segment: Aon United. In addition, the Company is continuing to expand on Aon United growth initiatives through its New Ventures Group.

In 2020, our consolidated total revenue was $11,066 million. This includes $4,690 million in Commercial Risk Solutions, $1,814 million in Reinsurance Solutions, $1,753 million in Retirement Solutions, $1,655 million in Health Solutions, and $1,171 million in Data & Analytic Services, before intercompany eliminations.

Principal Products and Services

Commercial Risk Solutions includes retail brokerage, cyber solutions, global risk consulting, and captives. In retail brokerage, our team of expert risk advisors applies a client-focused approach to commercial risk products and services that leverage Aon’s global network of resources, industry-leading data and analytics, and specialized expertise. Cyber solutions is one of the industry’s premier resources in cyber risk management. Our strategic focus extends to identify and protect critical digital assets supported by best-in-class transactional capabilities, enhanced coverage expertise, deep carrier relationships, and incident response expertise. Global risk consulting is a world-leading provider of risk consulting services supporting clients to better understand and manage their risk profile through identifying and quantifying the risks they face. We assist clients with the selection and implementation of the appropriate risk transfer, risk retention, and risk mitigation solutions, and ensure the continuity of their operations through claims consulting. Captives is a leading global captive insurance solutions provider that manages over 1,100 insurance entities worldwide including captives, protected segregated and incorporated cell facilities, as well as entities that support insurance-linked securities and specialist insurance and reinsurance companies.

Reinsurance Solutions includes treaty and facultative reinsurance and capital markets. Treaty reinsurance addresses underwriting and capital objectives on a portfolio level, allowing our clients to more effectively manage the combination of premium growth, return on capital, and rating agency interests on an integrated basis. This includes the development of more competitive, innovative, and efficient risk transfer options. Facultative reinsurance empowers clients to better understand, manage, and transfer risk through innovative facultative solutions and provides the most efficient access to the global facultative reinsurance markets. Capital markets is a global investment bank with expertise in insurance-linked securities, capital raising, strategic advice, restructuring, and mergers and acquisitions. We partner with insurers, reinsurers, investment firms, and corporations in executing innovative risk management products, capital market solutions and corporate finance advisory services.

Retirement Solutions includes core retirement, investment consulting, and human capital. Retirement consulting specializes in providing organizations across the globe with strategic design consulting on their retirement programs, actuarial services, and risk management, including pension de-risking, governance, integrated pension administration, and legal and compliance consulting. Investment consulting provides public and private companies and other institutions with advice on developing and maintaining investment programs across a broad range of plan types, including defined benefit plans, defined contribution plans, endowments, and foundations. Within investment consulting, our delegated investment solutions offer ongoing management of investment programs and fiduciary responsibilities either in a partial or full discretionary model for multiple asset owners. It partners with clients to deliver our scale and experience to help them effectively manage their investments, risk, and governance and potentially lower costs. Human capital delivers advice and solutions that help clients accelerate business outcomes by improving the performance of their people including, assessment, optimized deployment, and the design, alignment, and benchmarking of compensation to business strategy and performance outcomes.

Health Solutions includes health and benefits brokerage and health care exchanges. Health and benefits brokerage partners with employers to develop innovative, customized benefits strategies that help manage risk, drive engagement, and promote accountability. Our private health exchange solutions help employers transform how they sponsor, structure, and deliver health benefits by building and operating a cost effective alternative to traditional employee and retiree health care. We seek outcomes of reduced employer costs, risk, and volatility, alongside greater coverage and plan choices for individual participants.

Data & Analytic Services includes Affinity, Aon Inpoint, CoverWallet, and ReView. Affinity specializes in developing, marketing and administering customized insurance programs and specialty market solutions for Affinity organizations and their members or affiliates. Aon Inpoint draws on the Global Risk Insight Platform, one of Aon’s proprietary databases, and is dedicated to making insurers, reinsurers. and other financial services participants more competitive by providing data, analytics, engagement, and consulting services. CoverWallet is a leading digital insurance platform for small- and medium-sized businesses dedicated to delivering exceptional client experiences to new and existing clients by leveraging data and analytics and a technology-enabled operating model to provide choice, transparency and convenience. ReView draws on another Aon proprietary database and broker market knowledge to provide advisory services, analysis, and benchmarking to help reinsurers more effectively meet the needs of cedents through the development of more competitive, innovative, and efficient risk transfer options.

Revenue and Compensation

Our business generates revenues primarily through commissions, compensation from insurance and reinsurance companies for services we provide to them, and fees from customers. Commissions and fees for brokerage services vary depending upon several factors, which may include the amount of premium, the type of insurance or reinsurance coverage provided, the particular services provided to a client, insurer, or reinsurer, and the capacity in which we act. Compensation from insurance and reinsurance companies includes: (1) fees for consulting and analytics services, and (2) fees and commissions for administrative and other services provided to or on behalf of insurers and reinsurers. Fees from clients for advice and consulting services are dependent on the extent and value of the services we provide. Payment terms are consistent with current industry practices.

Fiduciary Funds

We typically hold funds on behalf of clients, including premiums received from clients and claims due to clients that are in transit to and from insurers. Certain funds held on behalf of clients are invested in interest-bearing premium trust accounts and can fluctuate significantly depending on when we collect and remit cash. The principal is segregated and not available for general operating purposes, although we earn interest on these accounts.

Competition

Our business operates in a highly competitive and fragmented environment. We compete with other global insurance brokers and consulting companies, including Marsh & McLennan Companies, Inc., WTW, and Arthur J Gallagher & Company, as well as numerous other global specialist, regional, and local firms in almost every area of our business. We also compete

with insurance and reinsurance companies that market and service their insurance products without the assistance of brokers or agents. Additionally, we compete with other businesses that do not fall into the categories above, including large financial institutions and independent consulting firms and consulting organizations affiliated with accounting, information systems, technology, and financial services firms.

Seasonality

Due to buying patterns and delivery of certain products in the markets we serve, revenues recognized tend to be higher in the first and fourth quarters of each fiscal year.

Licensing and Regulation

Our business activities are subject to licensing requirements and extensive regulation under the laws of countries in which we operate, including U.S. federal and state laws. See the “Risk Factors” section in Part I, Item 1A of this report for information regarding how actions by regulatory authorities or changes in legislation and regulation in the jurisdictions in which we operate may have an adverse effect on our business.

Regulatory authorities in the countries and states in the U.S. in which our operating subsidiaries conduct business may require individual or company licenses to act as producers, brokers, agents, third-party administrators, managing general agents, reinsurance intermediaries, or adjusters. Under the laws of most countries and states, regulatory authorities have relatively broad discretion with respect to granting, renewing, and revoking producers’, brokers’, and agents’ licenses to transact business in the country or state. The operating terms may vary according to the licensing requirements of the particular country or state, which may require, among other things, that a firm operates in the country or state through a local corporation. In a few countries and states, licenses may be issued only to individual residents or locally owned business entities. In such cases, our subsidiaries either have such licenses or have arrangements with residents or business entities licensed to act in the country or state.

Our subsidiaries must comply with laws and regulations of the jurisdictions in which they do business. These laws and regulations are enforced by the Financial Conduct Authority (“FCA”) in the U.K., by federal and state agencies in the U.S., and by various regulatory agencies and other supervisory authorities in other countries through the granting and revoking of licenses to do business, the licensing of agents, the monitoring of trade practices, policy form approval, limits on commission rates, and mandatory remuneration disclosure requirements.

Insurance authorities in the U.K., U.S., and certain other jurisdictions in which our subsidiaries operate have enacted laws and regulations governing the investment of funds, such as premiums and claims proceeds, held in a fiduciary capacity for others. These laws and regulations generally require the segregation of these fiduciary funds and limit the types of investments that may be made with them.

Investment, securities, and futures licensing authorities also govern certain business activities. For example, in the U.S., we use Aon Securities, LLC, an indirect, wholly owned subsidiary of Aon, and a U.S.-registered broker-dealer and investment advisor, member of the Financial Industry Regulatory Authority (“FINRA”) and Securities Investor Protection Corporation, for capital management transaction and advisory services and other broker-dealer activities. Similar operations exist in other jurisdictions outside of the U.S.

Further, pension and financial laws and regulations, including oversight and supervision by the FCA in the U.K., the SEC in the U.S., and regulators in other countries govern certain of the retirement-related consulting services provided by Aon and its subsidiaries and affiliates. This includes Aon subsidiaries that provide investment advisory services regulated by various U.S. federal authorities including the SEC and FINRA, as well as authorities on the state level. In addition, other services provided by Aon and its subsidiaries and affiliates, such as trustee services and retirement and employee benefit program administrative services, are subject in various jurisdictions to pension, investment, securities, and insurance laws and regulations, and supervision.

Clientele

Our clients operate in many businesses and industries throughout the world. No one client accounted for more than 2% of our consolidated total revenues in 2020. Additionally, we place insurance with many insurance carriers, none of which individually accounted for more than 10% of the total premiums we placed on behalf of our clients in 2020.

Human Capital Management

Aon United, Our Culture and Human Capital Strategy

Our colleagues are the cornerstone of Aon's success. Collaboration and innovation drive our culture, bringing the best of Aon to clients in a holistic and seamless manner. We approach every aspect of our business based on our Aon United Blueprint. Colleagues are trained upon hire under our Aon Impact Model, which supports the belief that businesses thrive when the people they serve flourish. The model sets behavioral expectations, embracing Aon's diverse capabilities, and shared cultural values to ensure colleagues are contributing towards a distinctive, high-performing, and inclusive Aon United culture.

Colleagues

As of December 31, 2020, we employed approximately 50,000 employees and conducted our operations in more than 120 countries and sovereignties. We know that our colleagues’ diverse talents, expertise, and insights contribute to the success of both our firm and our clients, and we seek to attract, grow, and retain the best talent in the industry. Our Colleague Mission is a central part of our Aon United Blueprint and is a key enabler to realizing our aspirations and purpose as a firm. We are committed to building thriving teams with the brightest talent, providing them opportunities to grow, rewarding them for their contributions, and supporting their journey to become the person and professional they want to be.

Pandemic Response

In 2020, we shifted the vast majority of our colleagues to remote work in response to the COVID-19 pandemic. The historic steps we’ve taken to build our Aon Business Services platform were instrumental in our response. Acting early, we began offering tools and services for enabling remote work and avoiding disruption in client service while emphasizing our commitment to colleague health and well-being. Our programs and policies on flexible work, leadership development, learning, telemedicine, childcare, sick leave, social and emotional health, rapidly evolved to meet the new normal and create a “new better” for our colleagues based on where they live and work.

Training and Development

We invest significant resources to develop the talent needed to remain at the forefront of innovation and make Aon an attractive employment destination. To make sure colleagues are on the right track for their career path, colleagues complete a variety of curricula to meet their career stage goals. We provide our colleagues what they need to learn, grow, and become the leaders our clients seek, and our communities need. From self-guided Aon University courses to our Leading Aon United and advanced learning programs, the curriculum is aligned to the Aon United Blueprint and the four expectations of the Aon Impact Model: Create Client Value, Develop Teams, Enable Innovation, and Deliver Business Results. Our use of virtual based learning and development programs during the COVID-19 pandemic has allowed us to continue these efforts despite most of our workforce being virtual during 2020.

Colleague Engagement and Retention

Providing an engaging and rewarding colleague experience is a top priority for our firm and understanding colleagues’ feedback helps us reach that goal. We use a variety of channels to facilitate open, on-going, and direct communication, including open forums with executives, pulse check surveys, and engagement through our Business Resource Groups, which are our independent, voluntary, non-profit associations that provide input, take action, and help identify opportunities for our firm to further its diversity, equity and inclusion commitments. In response to the challenging events of 2020, we updated our engagement survey process by offering more frequent pulse check surveys to understand how colleagues are engaging with their teams, the firm, and clients, so we can gather insights more rapidly and take timely action to address feedback. The pulse check surveys for 2020 have been focused on topics such as manager and leadership support, especially in how we serve clients; colleague well-being, inclusion and diversity; and the Aon United Blueprint. This feedback provides management a better understanding of evolving colleague viewpoints, and ensures we are taking appropriate steps to drive colleague engagement and retention. For discussion of the risks related to the attraction and retention of senior management and other professional personnel, see Part I, Item 1A. “Risk Factors” in this report.

Rewards

In addition to an inspired purpose and culture, we are proud to offer our colleagues a total rewards program that combines competitive pay, incentive opportunities, and benefits. Our compensation programs, including salary, recognition, cash and equity incentives, connect to our formal performance management and career development approach and serve to reward colleagues for their impact both in what they accomplish for clients, colleagues, and shareholders and how they achieve those results. We maintain a global commitment to colleague well-being and play a key role in supporting colleagues across the physical, emotional, financial, and social spectrum. Our comprehensive benefit programs are competitive for the markets in which we operate and aligned with our values and culture.

Inclusion and Diversity

A diverse and inclusive workforce is a business imperative and key to Aon’s long-term success. We emphasize the recruitment, hiring, development, and retention of diverse talent, including women and underrepresented groups. To recruit and hire a diverse community of the best talent, we’ve built partnerships with a wide range of organizations, schools, and universities, and we specifically source talent from diverse communities. Aon is committed to creating a workplace environment that fosters mutual dignity, respect, and equal employment opportunity. We have formal initiatives and policies designed to promote an inclusive workplace free of discrimination and harassment, where colleagues are treated and compensated fairly and equitably. Along with policies and initiatives, we encourage colleague input and action to make sure we create the diverse and inclusive workplace to which we aspire. The commitment starts at the top with our Board of Directors and the standing Inclusion and Diversity Sub-Committee of the Board. Our Global Inclusive Leadership Council is chaired by our Chief Executive Officer and Chief People Officer. Regional Inclusive Leadership Councils and colleague-led Business Resource Groups support execution and provide additional opportunities for colleagues to lead the firm to achieve a truly inclusive environment. We are focused on being a firm that is representative of the communities in which we operate. We believe diversity drives insight, and that by giving all talent a voice, we are encouraging the development of top talent that will produce the best outcomes for clients.

Our Apprenticeship Program

Apprenticeship programs help build a talent pipeline of highly skilled and diverse professionals while providing apprentices with advanced education and work experience. By removing some of the traditional barriers to entry-level employment, Aon can contribute to local workforce development and cultivate talent while improving retention rates in these entry-level roles.

Aon's two-year Apprenticeship Program, which was implemented in the U.S. and U.K. in 2017 and 2012, respectively, serves as an alternate route into a permanent role that normally requires a specific degree or professional experience by providing motivated, high-potential individuals with the required training (on the job and in the classroom), professional skills development, mentorship, and experiential learning to bridge the gap. Over 290 Aon apprentices have been hired since the inception of the program across the U.S. and U.K. Both programs are certified apprenticeship programs, by the Department of Labor in the U.S. and the Department of Education in the U.K. In 2020 we announced our commitment to expand this program to include additional U.S. cities outside of Chicago's metropolitan area to the following six metropolitan areas hiring over 100 apprentices: Houston, Minneapolis, New York, Philadelphia, San Francisco, and Washington, DC.

Website Access to Reports and Other Information

Our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and all amendments to those reports are made available free of charge through our website (http://www.aon.com) as soon as reasonably practicable after such material is electronically filed with or furnished to the SEC. Also posted on our website are the charters for our Audit, Compliance, Organization and Compensation, Governance/Nominating, Finance, and Inclusion & Diversity Committees, our Governance Guidelines, and our Code of Business Conduct. Within the time period required by the SEC and the New York Stock Exchange (“NYSE”), we will post on our website any amendment to or waiver of the Code of Business Conduct applicable to any executive officer or director. In addition, we may announce material information to investors and the marketplace using our investor relations website. While not all of the information that we post to such website is of a material nature, some information could be deemed to be material. Accordingly, we encourage investors, the media, and others interested in our company to review the information that we share at our investor relations link located at the bottom of the page on www.aon.com. The information provided on our website is not part of this report and is therefore not incorporated herein by reference.

Risk Factors Summary

The risk factors set forth below reflect risks associated with our businesses and the industries in which we operate generally. Some of the more significant risk factors are summarized below.

Risks Related to Our Business

• An overall decline in economic and business activity could have a material adverse effect on the financial condition and results of operations of our business.

• If our clients are not satisfied with our services, we may face additional cost, loss of profit opportunities, damage to our reputation, or legal liability.

• Revenues from commission arrangements may fluctuate due to many factors, including cyclical or permanent changes in the insurance and reinsurance markets outside of our control.

Financial Risks

• We are exposed to fluctuations in currency exchange rates that could negatively impact our financial results and cash flows. Similarly, changes in interest rates and deterioration of credit quality could reduce the value of our cash balances and investment portfolios and adversely affect our financial condition or results.

• A decline in the credit ratings of our senior debt and commercial paper may adversely affect our borrowing costs, access to capital, and financial flexibility.

• Our global effective tax rate is subject to a variety of different factors, which could create volatility in that tax rate, expose us to greater than anticipated tax liabilities, or cause us to adjust previously recognized tax assets and liabilities.

• We are a holding company and, therefore, may not be able to receive dividends or other payments in needed amounts from our subsidiaries.

Legal and Regulatory Risks

• We are subject to E&O claims against us as well as other contingencies and legal proceedings, some of which, if determined unfavorably to us, could have a material adverse effect on our financial condition or results of operations.

• Our businesses are subject to extensive governmental regulation, which could reduce our profitability, limit our growth, or subject us to legal and regulatory actions.

Operational Risks

• Our results of operations have been adversely affected and could be materially adversely affected in the future by the COVID-19 global pandemic.

• Our success depends on our ability to retain, attract and develop experienced and qualified personnel, including our senior management team and other professional personnel.

Risks Related to Technology, Cybersecurity, and Data Protection

• We rely on complex information technology systems and networks to operate our business. Any significant system or network disruption due to a breach in the security of our information technology systems could have a negative impact on our reputation, operations, sales, and operating results.

• Improper disclosure of confidential, personal, or proprietary data could result in regulatory scrutiny, legal liability, or harm to our reputation.

Risks Related to the Combination

• The Combination is subject to customary closing conditions, including conditions related to regulatory approvals, and may not be completed on a timely basis, or at all, or may be completed on a basis that has a material impact on the value of the combined company. Failure to close the Combination could negatively impact our share price and future business and financial results.

• While the Combination is pending, we are subject to business uncertainties related to our relationships with employees, clients and suppliers, which could adversely affect our business and operations. These uncertainties could also adversely affect the combined company following the Combination.

Risks Related to Being a Non-U.S. Company

• We are incorporated in Ireland, and Irish law differs from the laws in effect in the U.S. and may afford less protection to holders of our securities.

• As an Irish public limited company, certain capital structure decisions regarding the Company will require the approval of shareholders, which may limit the Company’s flexibility to manage its capital structure.

Risk Factors

The risk factors set forth below reflect risks associated with our existing and potential businesses and the industries in which we operate generally and contain “forward-looking statements” as discussed in the “Business” Section of Part I, Item 1 of this report. Readers should consider these risks in addition to the other information contained in this report because our business, financial condition, or results of operations could be materially adversely affected if any of these risks were to actually

occur and the occurrence of such risks could cause our actual results to differ materially from those stated in or implied by the forward-looking statements in this document and elsewhere.

Risks Related to Our Business

An overall decline in economic and business activity could have a material adverse effect on the financial condition and results of operations of our business.

The results of our operations are generally affected by the level of business activity of our clients, which in turn is affected by the economy of the industries and markets these clients serve. Economic downturns, volatility, or uncertainty in the broader economy or in specific markets may cause reductions in technology and discretionary spending by our clients, which may result in reductions in the growth of new business or reductions in existing business. If our clients become financially less stable, enter bankruptcy, liquidate their operations or consolidate, our revenues and collectability of receivables could be adversely affected.

The demand for property and casualty insurance generally rises as the overall level of economic activity increases and generally falls as such activity decreases, affecting both the commissions and fees generated by our Commercial Risk Solutions, Reinsurance Solutions, and Data and Analytic Service lines. The economic activity that impacts property and casualty insurance is most closely correlated with employment levels, corporate revenues, and asset values. Downward fluctuations in the year-over-year insurance premiums charged by insurers to protect against the same risk, referred to in the industry as softening of the insurance market, could adversely affect these businesses as a significant portion of the earnings are determined as a percentage of premiums charged to our clients. Insolvencies and consolidations associated with an economic downturn, especially insolvencies in the insurance industry, could adversely affect our brokerage business through the loss of clients by hampering our ability to place insurance and reinsurance business. Also, error and omission claims against us, which we refer to as E&O claims, may increase in economic downturns, also adversely affecting our business.

We face significant competitive pressures from traditional and non-traditional competitors that could affect our market share.

As a global professional services firm, we compete with global, national, regional, and local insurance companies that market and service their own products, other financial services providers, brokers, and investment managers, independent firms, and consulting organizations affiliated with accounting, information systems, technology, and financial services firms. We compete with respect to service, delivery of insights, product features, price, commission structure, technology, financial strength, ability to access certain insurance markets, and name recognition. Our competitors may have better financial, technical and marketing resources, broader customer bases, greater name recognition, more comprehensive products, stronger presence in certain geographies, or more established relationships with their customers and suppliers than we have.

In addition, alliances among competitors or mergers of competitors could affect our market share, and some of our competitors may hav

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None.

We have offices in various locations throughout the world. Substantially all of our offices are located in leased premises. We maintain our corporate headquarters at Metropolitan Building, James Joyce Street, Dublin 1, Ireland, where we occupy approximately 43,000 square feet of space under an operating lease agreement that expires in 2032. The following are additional significant leased properties, along with the occupied square footage and expiration.

As leases expire, we do not anticipate difficulty in negotiating renewals or finding other satisfactory space if the premise becomes unavailable. We believe that the facilities we currently occupy are adequate for the purposes for which they are being used and are well maintained. In certain circumstances, we may have unused space and may seek to sublet such space to third parties, depending upon the demands for office space in the locations involved. Due to COVID-19, the vast majority of colleagues are working remotely. We will reoccupy our remaining offices as local mandates are lifted and once protocols are in place to ensure a safe work environment. See Note 9 “Lease Commitments” of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report for information with respect to our lease commitments as of December 31, 2020.

We hereby incorporate by reference Note 16 “Claims, Lawsuits, and Other Contingencies” of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report.

Not applicable.

Information about our Executive Officers

The executive officers of Aon, as of February 19, 2021 unless otherwise noted, their business experience during a period of the last five years or longer, and their ages and positions held are set forth below.

PART II

Our Class A Ordinary Shares, $0.01 nominal value per share, are traded on the NYSE under the trading symbol AON.

On February 18, 2021, the last reported sale price of our ordinary shares as reported by the NYSE was $227.26 per share. We have approximately 375 holders of record of our Class A Ordinary Shares as of February 18, 2021.

The following information relates to the repurchases of equity securities by Aon or any affiliated purchaser during any month within the fourth quarter of the fiscal year covered by this report:

(1)Does not include commissions or other costs paid to repurchase shares.

(2)The Repurchase Program was established in April 2012 with $5.0 billion in authorized repurchases, and was increased by $5.0 billion in authorized repurchases in each of November 2014, June 2017, and November 2020 for a total of $20.0 billion in repurchase authorizations.

Information relating to the compensation plans under which equity securities of Aon are authorized for issuance is set forth under Part III, Item 12 “Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters” of this report and is incorporated herein by reference.

We did not make any unregistered sales of equity in 2020.

In connection with the Ireland Reorganization, the Class A ordinary shares of Aon Global Limited were cancelled and the holders thereof were issued an aggregate of approximately 231 million Class A ordinary shares of Aon plc. The terms and conditions of the issuance were sanctioned by the High Court of Justice in England and Wales after a hearing upon the fairness thereof at which all shareholders of Aon Global Limited had a right to appear and of which adequate notice had been given. The issuance was exempt from the registration requirements of the Securities Act of 1933, as amended, by virtue of Section 3(a)(10) thereof.

Not applicable.

EXECUTIVE SUMMARY OF 2020 FINANCIAL RESULTS

Aon is a leading global professional services firm providing a broad range of risk, retirement, and health solutions underpinned by proprietary data and analytics. Management continues to lead its set of initiatives designed to strengthen Aon and unite the firm with one portfolio of capability enabled by proprietary data and analytics and one operating model to deliver additional insight, connectivity, and efficiency.

Financial Results

The following is a summary of our 2020 financial results from continuing operations:

• Revenue increased $53 million, or 0%, to $11,066 million in 2020 compared to 2019, reflecting 1% organic revenue growth, offset by a 1% unfavorable impact from divestitures, net of acquisitions. Organic revenue growth for the year was driven by strength in the core portions of the business, partially offset by a decline in the more discretionary portions.

• Operating expenses decreased $559 million, or 6%, to $8,285 million in 2020 compared to 2019 due primarily to a $451 million decrease in restructuring charges, a $138 million decrease from accelerated amortization related to certain tradenames that were fully amortized in the second quarter, expense discipline in an effort to proactively manage liquidity due to uncertainties surrounding COVID-19 and its impact on the Company, including lower travel and entertainment expense, and a $42 million favorable impact from translating prior year period results at current period foreign exchange rates (“foreign currency translation”), partially offset by $123 million of transaction costs related to the pending combination with WTW and a $37 million increase in expenses related to acquisitions, net of divestitures.

• Operating margin increased to 25.1% in 2020 from 19.7% in 2019. The increase in operating margin from the prior year is primarily driven by organic revenue growth of 1% and a decrease in operating expenses as listed above.

• Due to the factors set forth above, net income from continuing operations was $2,017 million in 2020, an increase of $443 million, or 28%, from 2019.

• Diluted earnings per share from continuing operations was $8.45 per share during the twelve months of 2020 compared to $6.37 per share for the prior year period.

• Cash flows provided by operating activities was $2,783 million in 2020, an increase of $948 million, or 52%, from $1,835 million in 2019, primarily due to working capital improvements, including improved collections and actions taken to proactively manage liquidity, a $288 million decrease in restructuring cash outlays, and strong operational improvement. The prior year period included approximately $130 million of net cash payments related to legacy litigation.

We focus on four key non-GAAP metrics that we communicate to shareholders: organic revenue growth (decline), adjusted operating margins, adjusted diluted earnings per share, and free cash flows. These non-GAAP metrics should be viewed in addition to, not instead of, our Consolidated Financial Statements and Notes thereto (the “Consolidated Financial Statements”). The following is our measure of performance against these four metrics from continuing operations for 2020:

• Organic revenue growth (decline), a non-GAAP measure defined under the caption “Review of Consolidated Results — Organic Revenue Growth (Decline),” was 1% in 2020, compared to 6% organic growth in the prior year. Organic revenue growth was driven by strength in the core portions of our business, partially offset by a decline in the more discretionary portions.

• Adjusted operating margin, a non-GAAP measure defined under the caption “Review of Consolidated Results — Adjusted Operating Margin,” was 28.5% in 2020, compared to 27.5% in the prior year. The increase in adjusted operating margin primarily reflects expense discipline, including lower travel and entertainment expense, increased operating leverage across the portfolio, and 1% organic revenue growth, partially offset by a $47 million decrease in fiduciary investment income and an unfavorable impact from foreign currency translation of $12 million.

• Adjusted diluted earnings per share from continuing operations, a non-GAAP measure defined under the caption “Review of Consolidated Results — Adjusted Diluted Earnings per Share,” was $9.81 per share in 2020, an increase of $0.64 per share, or 7%, from $9.17 per share in 2019. The increase in adjusted diluted earnings per share primarily reflects strong operational performance and effective capital management, highlighted by $1.8 billion of share repurchase during 2020, partially offset by an unfavorable impact from foreign currency translation.

• Free cash flow, a non-GAAP measure defined under the caption “Review of Consolidated Results — Free Cash Flow,” was $2,642 million in 2020, an increase of $1,032 million, or 64%, from $1,610 million in 2019, driven by an increase of $948 million in cash flows from operations and a $84 million decrease in capital expenditures. The prior year included $75 million of capital expenditures related to the restructuring program.

IRELAND REORGANIZATION

For a description of the Ireland Reorganization, see Part I, Item 1. “Business - Ireland Reorganization” in this report.

BUSINESS COMBINATION AGREEMENT

On March 9, 2020, Aon and WTW, entered into a Business Combination Agreement with respect to a combination of the parties. At the effective date of the Combination, WTW shareholders will be entitled to receive 1.08 newly issued Class A ordinary shares of Aon in exchange for each ordinary share of WTW held by such holders. The Combination is subject to Irish Takeover Rules. The Business Combination Agreement contains certain operating covenants relating to the conduct of business of both parties in the interim period until the transaction is completed. These covenants require both parties to operate their respective businesses in all material respects in the ordinary course of business consistent with past practice. In addition, these covenants restrict each party from engaging in certain actions unless a party obtains the prior written consent of the other party. These actions relate to, among other things, authorizing or paying dividends above a specified rate; issuing or authorizing for issuance additional securities; salary, benefits or other compensation and employment-related matters; capital management, debt and liquidity matters; engaging in mergers, acquisitions and dispositions; entering into or materially modifying material agreements; entering into material litigation-related settlements; and making other corporate, tax and accounting changes. The parties’ respective shareholders approved the Combination on August 26, 2020. On October 30, 2020, Aon and WTW amended the Business Combination Agreement to provide that, at the effective date of the transaction, there will be 12 members of Aon’s Board of Directors, including one director mutually agreed by the parties.

The parties continue to work with regulators, including the Antitrust Division of the U.S. Department of Justice (which, as previously disclosed, has delivered a “Second Request” pursuant to the HSR Act) and the European Commission (which, as previously disclosed, has initiated a Phase II review of the Combination) to obtain the required approvals to close the Combination. Aon expects to close the Combination in the first half of 2021, subject to regulatory approval and customary closing conditions.

RECENT DEVELOPMENTS

The outbreak of the coronavirus, COVID-19, was declared by the World Health Organization to be a pandemic and has continued to spread across the globe, impacting almost all countries, in varying degrees, creating significant public health concerns, and significant volatility, uncertainty and economic disruption in every region in which we operate. While countries are in various stages of business and travel restriction

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We are exposed to potential fluctuations in earnings, cash flows, and the fair values of certain of our assets and liabilities due to changes in interest rates and foreign exchange rates. To manage the risk from these exposures, we enter into a variety of derivative instruments. We do not enter into derivatives or financial instruments for trading or speculative purposes.

The following discussion describes our specific exposures and the strategies we use to manage these risks. Refer to Note 2 “Summary of Significant Accounting Principles and Practices” of the Notes to Consolidated Financial Statements in Part II, Item 8 of this report for a discussion of our accounting policies for financial instruments and derivatives.

Foreign Exchange Risk

We are subject to foreign exchange rate risk. Our primary exposures include exchange rates between the U.S. dollar and the euro, the British pound, the Canadian dollar, the Australian dollar, the Indian rupee, and the Japanese yen. We use over-the-counter options and forward contracts to reduce the impact of foreign currency risk to our financial statements.

Additionally, some of our non-U.S. brokerage subsidiaries receive revenue in currencies that differ from their functional currencies. Our U.K. subsidiaries earn a portion of their revenue in U.S. dollars, euro, and Japanese yen, but most of their expenses are incurred in British pounds. At December 31, 2020, we have hedged approximately 45% of our U.K. subsidiaries’ expected exposures to the U.S. dollar, euro, and Japanese yen transactions for the years ending December 31, 2021 and 2022. We generally do not hedge exposures beyond three years.

We also use forward and option contracts to economically hedge foreign exchange risk associated with monetary balance sheet exposures, such as intercompany notes and current assets and liabilities that are denominated in a non-functional currency and are subject to remeasurement.

The potential loss in future earnings from foreign exchange derivative instruments resulting from a hypothetical 10% adverse change in year-end exchange rates would be $28 million and $14 million at December 31, 2021 and 2022, respectively.

The translated value of revenues and expenses from our international brokerage operations are subject to fluctuations in foreign exchange rates. If we were to translate prior year results at current year exchange rates, diluted earnings per share would have an unfavorable $0.03 impact during the twelve months ended December 31, 2020. Further, adjusted diluted earnings per share, a non-GAAP measure as defined and reconciled under the caption “Review of Consolidated Results — Adjusted Diluted Earnings Per Share,” would have an unfavorable $0.04 impact during the twelve months ended December 31, 2020 if we were to translate prior year results at current quarter exchange rates.

Interest Rate Risk

Our fiduciary investment income is affected by changes in international and domestic short-term interest rates. We monitor our net exposure to short-term interest rates and, as appropriate, hedge our exposure with various derivative financial instruments. This activity primarily relates to brokerage funds held on behalf of clients in the U.S. and in continental Europe. A hypothetical, instantaneous parallel decrease in the year-end yield curve of 100 basis points would cause a decrease, net of derivative positions, of $58 million to each of 2021 and 2022 pretax income. A corresponding increase in the year-end yield curve of 100 basis points would cause an increase, net of derivative positions, of $58 million to each of 2021 and 2022 pre-tax income.

We have long-term debt outstanding, excluding the current portion, with a fair market value of $8.8 billion and $7.4 billion as of December 31, 2020 and December 31, 2019, respectively. The fair value was greater than the carrying value by $1,471 million at December 31, 2020, and $815 million greater than the carrying value at December 31, 2019. A hypothetical 1% increase or decrease in interest rates would change the fair value by a decrease of 7% or an increase of 8%, respectively, at December 31, 2020.

We have selected hypothetical changes in foreign currency exchange rates, interest rates, and equity market prices to illustrate the possible impact of these changes; we are not predicting market events.

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Shareholders of Aon plc

Opinion on the Financial Statements

We have audited the accompanying consolidated statement of financial position of Aon plc (the Company) as of December 31, 2020 and 2019, the related consolidated statements of income, comprehensive income, shareholders’ equity and cash flows for each of the three years in the period ended December 31, 2020, and the related notes (collectively referred to as the “financial statements”). In our opinion, the financial statements present fairly, in all material respects, the consolidated financial position of the Company at December 31, 2020 and 2019, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2020, in conformity with U.S. generally accepted accounting principles.

We also have 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, 2020, based on criteria established in Internal Control-Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 framework), and our report dated February 19, 2021, expressed an unqualified opinion thereon.

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 the critical audit matter does not alter in any way our opinion on the consolidated 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 account or disclosure to which it relates.

We have served as the Company’s auditor since 1986.

Chicago, Illinois

February 19, 2021

Aon plc

Consolidated Statements of Income

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None.

Evaluation of Disclosure Controls and Procedures

We have conducted an evaluation of the effectiveness of the design and operation of our disclosure controls and procedures, as defined in Rules 13a-15(e) and 15d-15(e) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”) as of the end of the period covered by this annual report of December 31, 2020. Based on this evaluation, our chief executive officer and chief financial officer concluded as of December 31, 2020 that our disclosure controls and procedures were effective such that the information relating to Aon, including our consolidated subsidiaries, required to be disclosed in our SEC reports is recorded, processed, summarized and reported within the time periods specified in SEC rules and forms, and is accumulated and communicated to Aon’s management, including our chief executive officer and chief financial officer, as appropriate to allow timely decisions regarding required disclosure.

Management’s Report on Internal Control Over Financial Reporting

Management of Aon plc is responsible for establishing and maintaining adequate internal control over financial reporting as defined in Rules 13a-15(f) and 15d-15(f) under the Exchange Act. The Company’s internal control over financial reporting is designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with U.S. GAAP. Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Under the supervision and with the participation of our senior management, including our Chief Executive Officer and Chief Financial Officer, we assessed the effectiveness of our internal control over financial reporting as of December 31, 2020. In making this assessment, we used the criteria set forth by the Committee of Sponsoring Organizations of the Treadway Commission (COSO) in the Internal Control — Integrated Framework (2013 Framework). Based on this assessment, management has concluded our internal control over financial reporting is effective as of December 31, 2020.

The effectiveness of our internal control over financial reporting as of December 31, 2020 has been audited by Ernst & Young, LLP, the Company’s independent registered public accounting firm, as stated in their report titled “Report of Independent Registered Public Accounting Firm on Internal Control over Financial Reporting.”

Changes in Internal Control Over Financial Reporting

No changes in Aon’s internal control over financial reporting (as defined in Rule 13a-15(f) under the Exchange Act) occurred during 2020 that have materially affected, or that are reasonably likely to materially affect, Aon’s internal control over financial reporting.

Report of Independent Registered Public Accounting Firm

To the Board of Directors and Shareholders of Aon plc

Opinion on Internal Control over Financial Reporting

We have audited Aon plc’s internal control over financial reporting as of December 31, 2020, based on criteria established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of the Treadway Commission (2013 Framework), (the COSO criteria). In our opinion, Aon plc (the Company) maintained, in all material respects, effective internal control over financial reporting as of December 31, 2020, based on the COSO criteria.

We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the consolidated statements of financial position of the Company as of December 31, 2020 and 2019, and the related consolidated statements of income, comprehensive income, shareholders' equity and cash flows for each of the three years in the period ended December 31, 2020, and the related notes and our report dated February 19, 2021 expressed an unqualified opinion thereon.

Basis for Opinion

The Company’s management is responsible for maintaining effective internal control over financial reporting and for its assessment of the effectiveness of internal control over financial reporting included in the accompanying Management’s Report on Internal Control Over Financial Reporting. Our responsibility is to express an opinion on the Company’s internal control over financial reporting based on our audit. 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 audit in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether effective internal control over financial reporting was maintained in all material respects.

Our audit included obtaining an understanding of internal control over financial reporting, assessing the risk that a material weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe that our audit provides a reasonable basis for our opinion.

Definition and Limitations of Internal Control Over Financial Reporting

A company’s internal control over financial reporting is a process designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles. A company’s internal control over financial reporting includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail, accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance with generally accepted accounting principles, and that receipts and expenditures of the company are being made only in accordance with authorizations of management and directors of the company; and (3) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the company’s assets that could have a material effect on the financial statements.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that controls may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

Chicago, Illinois

February 19, 2021

Not applicable.

PART III

Information relating to Aon’s directors is set forth under the heading “Proposal 1 — Resolutions Regarding the Election of Directors” in the Proxy Statement for the 2021 Annual General Meeting of Shareholders (the “Proxy Statement”) and is incorporated herein by reference. Information relating to Aon’s executive officers is set forth in Part I of this report and is incorporated herein by reference. The remaining information required by this item is set forth under the headings “Corporate Governance” and “Board of Directors and Committees” in the Proxy Statement, and all such information is incorporated herein by reference.

We have adopted a code of ethics that applies to the Company’s directors, officers, and employees, including the Chief Executive Officer, Chief Financial Officer, Controller, and Chief Accounting Officer and other persons performing similar functions. The text of our code of ethics, which we call our Code of Business Conduct, is available on our website as disclosed in Part 1 of this report. We will provide a copy of the code of ethics without charge upon request to the Company Secretary, Metropolitan Building, James Joyce Street, Dublin 1, Ireland. We will disclose on our website any amendment to or waiver from our code of ethics on behalf of any of our executive officers or directors.

Information relating to director and executive officer compensation is set forth under the headings “Compensation Committee Report,” “Compensation Discussion and Analysis,” and “Executive Compensation” in the Proxy Statement, and all such information is incorporated herein by reference.

The material incorporated herein by reference to the information set forth under the heading “Compensation Committee Report” in the Proxy Statement shall be deemed furnished, and not filed, in this Form 10-K and shall not be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act as a result of this furnishing, except to the extent that it is specifically incorporated by reference by Aon.

Information relating to compensation committee interlocks and insider participation is set forth under the heading “Compensation Discussion and Analysis - Compensation Committee Interlocks and Insider Participation” in the Proxy Statement and is incorporated herein by reference.

Information relating to equity compensation plans and the security ownership of certain beneficial owners and management of Aon plc’s ordinary shares is set forth under the headings “Equity Compensation Plan Information,” “Principal Holders of Voting Securities,” and “Security Ownership of Directors and Executive Officers” in the Proxy Statement, and all such information is incorporated herein by reference.

Information required by this Item is included under the headings “Corporate Governance — Director Independence” and “Certain Relationships and Related Transactions” in the Proxy Statement and is incorporated herein by reference.

Information required by this Item is included under the heading “Auditor Fees” in the Proxy Statement and is incorporated herein by reference.

PART IV

The following document has been included in Part II, Item 9.

All schedules for the Registrant and consolidated subsidiaries have been omitted because the required information is not present in amounts sufficient to require submission of the schedules or because the information required is included in the respective financial statements or notes thereto.

• Document has been previously filed with the Securities and Exchange Commission and is incorporated herein by reference herein. Unless otherwise indicated, such document was filed under Commission File Number 001-07933.

Indicates a management contract or compensatory plan or arrangement.

The registrant agrees to furnish to the Securities and Exchange Commission upon request a copy of (1) any long-term debt instruments that have been omitted pursuant to Item 601(b)(4)(iii)(A) of Regulation S-K, and (2) any schedules omitted with respect to any material plan of acquisition, reorganization, arrangement, liquidation or succession set forth above.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.