UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 ____________________________________________________________________________ FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE FISCAL YEAR ENDED DECEMBER 31, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number: 1-7933 ___________________________________________________________________________________________ Aon plc (Exact name of registrant as specified in its charter) IRELAND 98-1539969 (State or other jurisdiction of (I.R.S. Employer incorporation or organization) Identification No.) 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: Title of Each Class Trading Symbol Name of Each Exchange on Which Registered Class A Ordinary Shares, $0.01 nominal value AON New York Stock Exchange 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 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. Large accelerated filer ☒ Accelerated filer ☐ Non-accelerated filer ☐ Smaller reporting company ☐ Emerging growth company ☐ 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: Name of each exchange Title of each class Trading Symbol(s) on which registered Class A Ordinary Shares, $0.01 nominal value AON New York Stock Exchange Guarantees of Aon plc’s 4.00% Senior Notes due 2023 AON23 New York Stock Exchange Guarantees of Aon plc’s 3.50% Senior Notes due 2024 AON24 New York Stock Exchange Guarantees of Aon plc’s 3.875% Senior Notes due 2025 AON25 New York Stock Exchange Guarantees of Aon plc’s 2.875% Senior Notes due 2026 AON26 New York Stock Exchange Guarantees of Aon plc’s 4.25% Senior Notes due 2042 AON42 New York Stock Exchange Guarantees of Aon plc’s 4.45% Senior Notes due 2043 AON43 New York Stock Exchange Guarantees of Aon plc’s 4.60% Senior Notes due 2044 AON44 New York Stock Exchange Guarantees of Aon plc’s 4.75% Senior Notes due 2045 AON45 New York Stock Exchange 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; 3 • 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,