Aon plc

Reconciliation of Non-GAAP Measures

Aon plc

Reconciliation of Non-GAAP Measures—Organic Revenue Growth and Free Cash Flow (Unaudited)

Organic Revenue Growth (Unaudited)

(1)

Currency impact represents the effect on prior year period results if they were translated at current period foreign exchange rates.

(2)

Fiduciary investment income for the twelve months ended December 31, 2025 and 2024 was $271 million and $315 million, respectively.

(3)

Organic revenue growth includes the impact of certain intercompany activity and excludes the impact of changes in foreign exchange rates, fiduciary investment income, acquisitions (provided that Organic revenue growth includes Organic growth of an acquired business as calculated assuming that the acquired business was part of the combined company for the same proportion of the relevant prior year period), divestitures (including held for sale disposal groups, which are adjusted from Organic revenue growth upon classification as held for sale, if any), transfers between revenue lines, and gains or losses on derivatives accounted for as hedges.

Free Cash Flow (Unaudited)

(1)

Free cash flow is defined as cash flows from operations less capital expenditures. This non-GAAP measure does not imply or represent a precise calculation of residual cash flow available for discretionary expenditures.

2026 Aon Proxy Statement A-1

Aon plc

Reconciliation of Non-GAAP Measures—Operating Income, Operating Margin, and Diluted Earnings Per Share (Unaudited)(1)

(1)

Certain noteworthy items impacting operating income in 2024 and 2023 are described in this schedule. The items shown with the caption “adjusted” are non-GAAP measures.

(2)

Segment expenses exclude governance costs, post-retirement benefits, and other costs that are not directly attributable to a specific segment.

(3)

Total charges are expected to include technology-related costs to facilitate streamlining and simplifying operations, headcount reduction costs, and costs associated with asset impairments, including real estate consolidation costs.

(4)

Transaction costs include advisory, legal, accounting, regulatory, and other professional or consulting fees required to complete the NFP Transaction. No transaction costs were recognized for the three and twelve months ended December 31, 2025. For the twelve months ended December 31, 2024, $90 million of transaction costs were recognized in Total operating expenses and $6 million were recognized in Other income (expense) related to the extinguishment of acquired NFP debt.

(5)

The NFP Transaction has and will continue to result in certain non-recurring integration costs associated with colleague severance, retention bonus awards, termination of redundant third-party agreements, costs associated with legal entity rationalization, and professional or consulting fees related to alignment of management processes and controls, as well as costs associated with the assessment of NFP information technology environment and security protocols. Aon incurred $77 million and $95 million of integration costs in the twelve months ended December 31, 2025 and 2024, respectively.

(6)

In the fourth quarter of 2023, Aon recognized a $197 million charge in connection with transactions for which capital was arranged by a third party, Vesttoo Ltd., and in the third quarter of 2025, certain legal settlement expenses and recoveries were recognized resulting in a $23 million reduction of expense within the Risk Capital segment.

A-2 2026 Aon Proxy Statement

(1)

Certain noteworthy items impacting operating income in 2025 and 2024 are described in this schedule. The items shown with the caption "adjusted" are non‑GAAP measures.

(2)

For the twelve months ended December 31, 2025 and 2024, Other income was $1.2 billion and $348 million, respectively. Adjusted other expense for the twelve months ended December 31, 2025 was $96 million compared to Adjusted other income of $13 million for the twelve months ended December 31, 2024.

(3)

Adjusted other income (expense) excluded gains related to deferred consideration from the affiliates of The Blackstone Group L.P. and the other designated purchasers related to a divestiture completed in a prior‑year period. During the twelve months ended December 31, 2025, a gain of $108 million was recognized, which was all recognized in the first six months of 2025. During the twelve months ended December 31, 2024, a gain of $84 million was recognized, which was all recognized in the first nine months of 2024.

(4)

Adjusted other income (expense) excluded gains from dispositions of $257 million related to the sale of a business for the twelve months ended December 31, 2024. For the twelve months ended December 31, 2025, Adjusted other income (expense) excluded gains from the disposal of NFP wealth totaling $1,199 million.

(5)

Adjusted other income (expense) excluded $6 million of debt extinguishment charges related to the repayment of NFP debt, which is considered a transaction related cost incurred in the second quarter of 2024.

(6)

Adjusted items are generally taxed at the estimated annual effective tax rate, except for the applicable tax impact associated with changes in the fair value of contingent consideration, certain legal settlements, Accelerating Aon United Program expenses, certain transaction and integration costs related to the acquisition of NFP, certain gains from dispositions, and deferred consideration from a prior‑year sale of business, which are adjusted at the related jurisdictional rate. The tax adjustment also excludes interest accruals for income tax reserves related to the termination fee payment made in connection with the Company’s terminated proposed combination with Willis Towers Watson.

2026 Aon Proxy Statement A-3

About Aon

Aon plc (NYSE: AON) exists to shape decisions for the better— to protect and enrich the lives of people around the world. Through actionable analytic insight, globally integrated Risk Capital and Human Capital expertise, and locally relevant solutions, our colleagues provide clients in over 120 countries with the clarity and confidence to make better risk and people decisions that help protect and grow their businesses.

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AON PLC MSC 17510, AON P.O. BOX 551343 ATLANTA, GA 30355 SCAN TO VIEW MATERIALS & VOTE VOTE BY INTERNET Before The Meeting - Go to www.proxyvote.com or scan the QR Barcode above Use the Internet to transmit your voting instructions and to receive electronic delivery of information up until 5:00 PM, Irish Standard Time on June 25, 2026, (or for shares held through the Canadian ESPP, no later than 4:59 AM Irish Standard Time on June 24, 2026). Have your proxy card in hand when you access the web site and follow the instructions to obtain your records and to create an electronic voting instruction form. You may vote in person at the Meeting if you attend in person. Have the information that is printed in the box marked by the arrow available and follow the instructions. You may attend the meeting virtually via webcast at www.virtualshareholdermeeting.com/AON2026. Note that attending the Meeting virtually will not allow you to vote at the Meeting. VOTE BY PHONE - 1-800-690-6903 Use any touch-tone telephone to transmit your voting instructions up until 5:00 PM, Irish Standard Time on June 25, 2026, (or for shares held through the Canadian ESPP, no later than 4:59 AM Irish Standard Time on June 24, 2026). Have your proxy card in hand when you call and then follow the instructions. VOTE BY MAIL Mark, sign and date your proxy card and return it in the postage-paid envelope we have provided or return it to Vote Processing, c/o Broadridge, 51 Mercedes Way, Edgewood, NY 11717. TO VOTE, MARK BLOCKS BELOW IN BLUE OR BLACK INK AS FOLLOWS: V92373-P49177 KEEP THIS PORTION FOR YOUR RECORDS THIS PROXY CARD IS VALID ONLY WHEN SIGNED AND DATED. DETACH AND RETURN THIS PORTION ONLY AON PLC The Board of Directors recommends a vote FOR all the nominees listed and FOR Proposals 2-7. 1. Election of Directors: 1a. Lester B. Knight 1b. Gregory C. Case 1c. Jose Antonio Álvarez 1d. Jin-Yong Cai 1e. Jeffrey C. Campbell 1f. Cheryl A. Francis 1g. Jo Ann Jenkins 1h. Adriana Karaboutis 1i. 1j. Richard C. Notebaert Gloria Santona 1k. Sarah E. Smith 1l. Byron O. Spruell 1m. James G. Stavridis For Against Abstain 2. Advisory resolution to approve the compensation of the Company’s named executive officers. 3. Ratify the appointment of Ernst & Young LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026. 4. Re-appoint Ernst & Young Chartered Accountants as the Company’s statutory auditor under Irish Law. 5. Authorize the Board or the Audit Committee of the Board to determine the remuneration of Ernst & Young Ireland, in its capacity as the Company’s statutory auditor under Irish Law. 6. Authorize the Board to issue Class A Ordinary Shares under Irish Law. 7. Authorize the Board to opt-out of statutory pre-emption rights under Irish Law. For Against Abstain NOTE: In their discretion, the Proxies are authorized to vote upon such other business as may properly come before the meeting or any adjournment or postponement thereof. Please sign exactly as your name(s) appear(s) hereon. When signing as attorney, executor, administrator, or other fiduciary, please give full title as such. Joint owners should each sign personally. All holders must sign. If a corporation or partnership, please sign in full corporate or partnership name by authorized officer. Signature [PLEASE SIGN WITHIN BOX] Date Signature (Joint Owners) Date

Important Notice Regarding the Availability of Proxy Materials for the Aon plc Annual General Meeting: The 2026 Proxy Statement, the 2025 Annual Report, and the 2025 Irish Financial Statements are available atwww.proxyvote.com. V92374-P49177 AON PLC Notice of 2026 Annual General Meeting of Shareholders Proxy Solicited by Board of Directors for Annual General Meeting – June 26, 2026 The Chair, Chief Executive Officer, Company Secretary, and any Assistant Company Secretary, are hereby authorized to represent and vote the shares of the undersigned, with all the powers which the undersigned would possess if personally present, at the Annual General Meeting of Shareholders of AON PLC to be held on June 26, 2026 or at any postponement or adjournment thereof. Shares represented by this proxy will be voted as directed by the shareholder. If no such directions are indicated, the Proxies will have authority to vote FOR the election of nominees listed in Proposal 1 and FOR Proposals 2-7. In their discretion, the Proxies are authorized to vote upon such other business as may properly come before the meeting. If you hold your shares in the AON PLC Canadian ESPP your vote must be received by 4:59 AM, Irish Standard Time on June 24, 2026. In the case of registered joint holders (i) only one need sign, and (ii) the vote of the senior holder who tenders a vote, whether in person or by proxy or (in the case of a corporation) by authorized representative, will alone be counted. For this purpose seniority will be determined by the order in which the names appear in the register of shareholders of AON PLC in respect of the joint holding. (Items to be voted appear on reverse side)