Executive Change · Reg FD Disclosure

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): March 14, 2025     Aon plc (Exact Name of Registrant as Specified in Charter)       Ireland   1-7933   98-1539969 (State or Other Jurisdiction of Incorporation)   (Commission File Number)   (IRS Employer Identification No.) 15 George’s Quay , Dublin 2 , Ireland D02 VR98 (Address of principal executive offices) (Zip Code) Registrant’s telephone number, including area code: + 353 1 266 6000 Not Applicable (Former Name or Former Address, if Changed Since Last Report)     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:   Title of each class   Trading Symbol(s)   Name of each exchange on which registered Class A Ordinary Shares $0.01 nominal value   AON   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 Corporation and Aon Global Holdings plc’s 2.85% Senior Notes due 2027   AON27   New York Stock Exchange Guarantees of Aon North America, Inc.’s 5.125% Senior Notes due 2027   AON27B   New York Stock Exchange Guarantees of Aon North America, Inc.’s 5.150% Senior Notes due 2029   AON29   New York Stock Exchange Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.05% Senior Notes due 2031   AON31   New York Stock Exchange Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.60% Senior Notes due 2031   AON31A   New York Stock Exchange Guarantees of Aon North America, Inc.’s 5.300% Senior Notes due 2031   AON31B   New York Stock Exchange Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.00% Senior Notes due 2032   AON32   New York Stock Exchange Guarantees of Aon Corporation and Aon Global Holdings plc’s 5.35% Senior Notes due 2033   AON33   New York Stock Exchange Guarantees of Aon North America, Inc.’s 5.450% Senior Notes due 2034   AON34   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 Guarantees of Aon Corporation and Aon Global Holdings plc’s 2.90% Senior Notes due 2051   AON51   New York Stock Exchange Guarantees of Aon Corporation and Aon Global Holdings plc’s 3.90% Senior Notes due 2052   AON52   New York Stock Exchange Guarantees of Aon North America, Inc.’s 5.750% Senior Notes due 2054   AON54   New York Stock Exchange 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 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers. On March 14, 2025 (the “Transition Date”), Eric Andersen transitioned to a new role as Senior Advisor and ceased to serve as President of Aon plc (the “Company”) and Aon Corporation in accordance with Section 5(a) of the employment agreement dated July 26, 2023, by and between Mr. Andersen and Aon Corporation, as filed as Exhibit 10.86 to the Company’s Annual Report on Form 10-K filed on February 18, 2025. Also on the Transition Date, Gregory C. Case, the Company’s Chief Executive Officer, assumed the additional title of President of the Company and Aon Corporation. Information regarding Mr. Case that is responsive to Items 401(b), (d), (e) and Item 404(a) of Regulation S-K is incorporated by reference herein from the Company’s definitive proxy statement on Schedule 14A filed with the Securities and Exchange Commission on April 29, 2024. On the Transition Date, the Company and Aon Corporation entered into an amendment (the “Amendment”) to the Amended and Restated Employment Agreement dated January 16, 2015, and amended April 20, 2018, May 15, 2018, July 26, 2021, and April 2, 2024, with Mr. Case. The Amendment reflects that Mr. Case has assumed the additional title of President and makes no changes to Mr. Case’s compensation arrangements. The foregoing summary is qualified in its entirety by reference to the Amendment, a copy of which is attached hereto as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated herein by reference.   Item 7.01. Regulation FD Disclosure. A copy of a press release issued by the Company on March 17, 2025, corresponding to the role transitions described above is furnished herewith as Exhibit 99.1. The information in this Item 7.01 of this Current Report, including Exhibit 99.1 hereto, is being furnished to the Securities and Exchange Commission and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section. This information shall not be deemed to be incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as shall be expressly set forth by specific reference in such a filing.   Item 9.01. Financial Statements and Exhibits (d) Exhibits   Exhibit Number    Exhibit Title or Description 10.1    Amendment to Employment Agreement, dated as of March 14, 2025, by and among Aon plc, Aon Corporation and Gregory C. Case. 99.1    Press Release issued by Aon plc on March 17, 2025. 104    Cover Page Interactive Data File (embedded within the Inline XBRL document) SIGNATURES Pursuant to the requirements 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.   Aon plc By:   /s/ Darren Zeidel Name:   Darren Zeidel Title:   Executive Vice President, General Counsel and Company Secretary Date: March 17, 2025