UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 1, 2020 Aon plc (Exact name of registrant as specified in its charter) Ireland 1-7933 98-1030901 (State or other jurisdiction (Commission (IRS Employer of incorporation) File Number) Identification No.) 122 Leadenhall Street, London, England EC3V 4AN (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: +44 20 7623 5500 Former name or former address, if changed since last report: Not Applicable Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2 below): ☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) ☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) ☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) ☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Trading Name of each exchange Title of each class Symbol(s) on which registered Class A Ordinary Shares, $0.01 nominal value AON New York Stock Exchange Guarantees of Aon plc’s 2.800% Senior Notes AON21 New York Stock Exchange due 2021 Guarantees of Aon plc’s 4.000% Senior Notes AON23 New York Stock Exchange due 2023 Guarantees of Aon plc’s 3.500% Senior Notes AON24 New York Stock Exchange due 2024 Guarantees of Aon plc’s 3.875% Senior Notes AON25 New York Stock Exchange due 2025 Guarantees of Aon plc’s 2.875% Senior Notes AON26 New York Stock Exchange due 2026 Guarantees of Aon plc’s 4.250% Senior Notes AON42 New York Stock Exchange due 2042 Guarantees of Aon plc’s 4.450% Senior Notes AON43 New York Stock Exchange due 2043 Guarantees of Aon plc’s 4.600% Senior Notes AON44 New York Stock Exchange due 2044 Guarantees of Aon plc’s 4.750% Senior Notes AON45 New York Stock Exchange due 2045 Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). 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. ☐ Item 8.01 Other Events. Rule 3-10 of Regulation S-X Aon plc, an Irish public limited company (the “Company”), is filing this Current Report on Form 8-K for the purpose of amending Note 19 (Guarantee of Registered Securities) and adding Note 21 (Subsequent Events) to the audited consolidated financial statements included in Part II, Item 8 of the Annual Report on Form 10-K for the year ended December 31, 2019 of Aon plc, a company incorporated under the laws of England and Wales (“Aon UK”), filed with the Securities and Exchange Commission on February 14, 2020 (the “Annual Report”). Pursuant to Rule 12g-3(a) promulgated under the Securities Exchange Act of 1934, as amended, the Company is the successor issuer to Aon UK. The Company is amending Note 19 to the audited consolidated financial statements to provide condensed consolidating financial information in accordance with Rule 3-10 of Regulation S-X because: (i) the debt securities of Aon UK are fully and unconditionally guaranteed by the Company, Aon Corporation, a Delaware corporation (“Aon Delaware”), and Aon Global Holdings Limited, a company incorporated under the laws of England and Wales (“AGH”); (ii) the debt securities of Aon Delaware are fully and unconditionally guaranteed by the Company, Aon UK and AGH; and (iii) the debt securities that may be issued by the Company, Aon UK or Aon Delaware may be fully and unconditionally guaranteed by the Company, Aon UK, Aon Delaware and/or AGH. To reflect this, Part II, Item 8 of the Annual Report is being amended in its entirety and is attached as Exhibit 99.1 to this Current Report on Form 8-K is and incorporated by reference herein. Because only Notes 19 and 21 to the audited financial statements are affected, the other information contained in the Annual Report remains unchanged. No attempt has been made in this Current Report on Form 8-K or in Exhibit 99.1 to this Current Report on Form 8-K to modify or update disclosures in the Annual Report, except with respect to the amendment of Note 19 and the addition of Note 21 to the audited financial statements as described above. Item 9.01 Financial Statements and Exhibits. (d) Exhibits Exhibit Number Description 23.1 Consent of Ernst & Young LLP 99.1 Update to the Annual Report on Form 10-K for the year ended December 31, 2019 of Aon UK SIGNATURES Pursuant to the requirement of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: April 1, 2020 AON PLC By: /s/ Molly Johnson Molly Johnson Assistant Company Secretary Exhibit 23.1 Ernst & Young LLP 155 N Wacker Drive Chicago, IL 60606 CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM We consent to the incorporation by reference in the following Registration Statements: Registration Statement Form Number Purpose S-8 333-55773 Pertaining to Aon’s stock award plan, stock option plan, and employee stock purchase plan S-4 333-168320 Pertaining to the registration of 4,545,566 shares on common stock registered on Post Effective Amendment No. 1 related to the Amended and Restated Global Stock and Incentive Compensation Plan of Hewitt Associates, Inc. S-8 333-103344 Pertaining to the Aon Stock Incentive Plan S-8 333-106584 Pertaining to Aon’s deferred compensation plan S-8 333-145928 Pertaining to the Aon Stock Incentive Plan S-8 333-145930 Pertaining to the registration of common stock underlying equity securities issued to Aon’s president and chief executive officer S-8 333-174788 Pertaining to Aon’s 2011 stock incentive plan and 2011 employee stock purchase plan S-4 333-178991 Pertaining to the registration of 355,110,708 Class A Ordinary Shares of Aon Global Limited, and in the related Proxy Statement / Prospectus of Aon Global and Aon Corporation contained therein S-3 333-227514 Pertaining to the registration of debt securities, guarantees, preference shares, Class A Ordinary Shares, Convertible Securities, share purchase contracts and share purchase units of Aon plc and debt securities and guarantees of Aon Corporation S-8 333-184999 Pertaining to Aon plc Company Share Save Plan S-8 333-199759 Pertaining to the registration of an additional 9,000,000 Class A Ordinary Shares to be issued pursuant to the Aon plc 2011 Incentive Plan S-8 333-235296 Pertaining to the registration of an additional 5,000,000 Class A Ordinary Shares to be issued pursuant to the Aon plc 2011 Incentive Plan of our report dated February 14, 2020 (except for Note 19 and Note 21, as to which the date is April 1, 2020), with respect to the consolidated financial statements of Aon plc, incorporated by reference in this Current Report (Form 8-K) dated April 1, 2020 of Aon plc. /s/ Ernst & Young LLP Chicago, Illinois April 1, 2020 A member firm of Ernst & Young Global Limited Exhibit 99.1 Item 8. Financial Statements and Supplementary Data Report of Independent Registered Public Accounting Firm The Board of Directors and Shareholders 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, 2019 and 2018, 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, 2019, 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, 2019 and 2018, and the consolidated results of its operations and its cash flows for each of the three years in the period ended December 31, 2019, and the related notes 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, 2019, 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 14, 2020, expressed an unqualified opinion thereon. Adoption of New Accounting Standards As discussed in Note 2 “Summary of Significant Accounting Principles and Practices” of the Notes to the Consolidated Financial Statements, the Company changed its method of accounting for leases in 2019. As discussed in Note 2 “Summary of Significant Accounting Principles and Practices” of the Notes to the Consolidated Financial Statements, the Company changed its method of accounting for revenue in 2018. Basis for Opinion These financial statements are the responsibility of the Company’s management.