2024 Proxy Statement

Notice of Annual General Meeting of Shareholders

We are pleased to invite you to join the board of directors (the "Board" or the "Board of Directors") and senior leadership at the Aon plc ("Aon" or the "Company") annual general meeting of shareholders (the "Annual Meeting") scheduled for Friday, June 21, 2024 at 8:30 a.m. Irish Standard Time.

Items of Business:

Shareholders are strongly encouraged to vote their shares by proxy in advance of the Annual Meeting by one of the methods described on pages 77-78 of the proxy statement. Shareholders who wish to attend the Annual Meeting virtually may do so via webcast at meetnow.global/MLDMKCM, as further described on page 79 of the proxy statement. Note that attending the Annual Meeting virtually will not allow you to vote at the Annual Meeting. During the Annual Meeting, the Board will present, for consideration by the shareholders, the Company's statutory financial statements under Irish law for the fiscal year ended December 31, 2023 (including the reports of the directors and the Irish statutory auditor thereon) and a review of the Company's affairs. We urge you to read the attached proxy statement for additional information concerning the matters to be considered at the Annual Meeting. The proxy statement shall be deemed incorporated into this notice.

Holders of Class A Ordinary Shares at the close of business on April 12, 2024 can vote at the Annual Meeting. A shareholder of record entitled to attend and vote at the Annual Meeting may appoint one or more proxies to attend, speak, and vote on his or her behalf by any of the procedures set out below and on pages 77-78 of the proxy statement. A proxy holder need not be a shareholder of record. To be valid, a proxy must be received by the Company using one of such procedures no later than 5:00 pm (Irish Standard Time) on June 20, 2024, the proxy deadline.

Important Notice Regarding the Availability of Proxy Materials for the Annual Meeting of Shareholders to be held on June 21, 2024.

The proxy statement and our Annual Report for the fiscal year ended December 31, 2023 are available at www.envisionreports.com/AON. Our Irish financial statements will be mailed to shareholders of record and made available at www.envisionreports.com/AON at least 21 days prior to the Annual Meeting. This notice and proxy statement are first being mailed or made available to shareholders on or about April 29, 2024.

By Order of the Board of Directors,

Darren Zeidel

Company Secretary

April 29, 2024

Proxy Summary

Voting Matters

Shareholders are being asked to vote on the following matters at the Annual Meeting:

4. Resolution to Re-Appoint Ernst & Young Ireland as the Company's Statutory Auditor FOR Under Irish law (page 66)

The Board believes that the continued retention of Ernst & Young Ireland to serve as our statutory auditor under Irish law from the conclusion of the Annual Meeting until the conclusion of the next annual general meeting of the Company is in the best interests of the Company and its shareholders.

We are providing the enclosed proxy materials to you in connection with the solicitation by the board of directors (the "Board") of Aon plc ("Aon" or the "Company") of proxies to be voted at the annual general meeting of shareholders to be held on June 21, 2024 (the "Annual Meeting"), or any adjournment or postponement thereof. The Annual Meeting will be held at 70 Sir John Rogerson's Quay, Dublin 2, Ireland. This proxy statement is first being mailed or made available to shareholders on or about April 29, 2024.

2023 Highlights

• Total revenue growth was 7% compared to 2022, reflecting organic revenue growth of 7%, driven by the ongoing strength of our Aon United strategy, and a 2% favorable impact from fiduciary investment income, partially offset by a 2% unfavorable impact from acquisitions, divestitures and other.
• Operating margin was 28.3% and adjusted operating margin was 31.6%, driven by revenue growth outpacing expense growth and long-term investments.
• Diluted earnings per share was $12.51 and adjusted diluted earnings per share was $14.14, reflecting strong operational performance and effective capital management, highlighted by $2.7 billion of share repurchases during 2023, partially offset by an unfavorable impact from higher non-cash pension expense and other non-operating expenses.
• Cash flows provided by operating activities was $3.4 billion in 2023, an increase of $216 million, or 7%, from $3.2 billion in 2022, reflecting strong operating income growth and overall working capital optimization, partially offset by higher cash tax payments and a negative impact to working capital due to temporary invoicing delays associated with the implementation of a new system. Free cash flow was $3.2 billion in 2023, an increase of $160 million, or 5%, from $3.0 billion in 2022, reflecting an increase in cash flows from operations, partially offset by a $56 million increase in capital expenditures.

Our Board of Directors

In January 2024, we announced that Jose Antonio Álvarez joined our Board effective January 24, 2024. Mr. Álvarez serves on the Audit Committee of the Board. In February 2024, we announced that Carolyn Y. Woo will be retiring from our Board effective at the Annual Meeting. Upon Dr. Woo's retirement, our Board will be composed of 12 directors, 11 of whom are independent, including the Board Chair. It is a priority of the Governance/Nominating Committee to continue to identify candidates for the Board of Directors who have diverse backgrounds and bring fresh perspectives to the Board.

Director Nominee Composition

*Directors who identify as Black or African American, Hispanic, Native American, Asian or Pacific Islander, or two or more races.

Diversity of Skills, Experience and Perspectives

Director Nominee Demographics

Racial/Ethnic Diversity

Asian

Black

Hispanic

White

Gender

Female

Male

• 2024 Aon Proxy Statement

Directors

Inclusion & Wellbeing Sub-Committee

Organization and Compensation Committee - Chair

Corporate Governance Highlights

Aon's commitment to good corporate governance is integral to our business. Highlights of our strong corporate governance practices include:

2023 Executive Compensation Highlights

The core principle of our executive compensation program continues to be pay for performance, as we continue towards our goal of being the leading global professional services firm focused on risk, health, and wealth.

Leadership Performance Program. In early 2024, we settled performance share units ("PSUs") granted to our NEOs in 2021 under our sixteenth LPP cycle ("LPP 16"). The settlement of those units in Class A Ordinary Shares was contingent upon achieving adjusted diluted earnings per share of at least $31.23 (threshold performance) over the performance period from January 1, 2021 to December 31, 2023, and reflects achievement of adjusted diluted earnings per share of $38.75, which exceeded the stretch performance level adjusted diluted earnings per share of $35.72. In 2023, we granted PSUs under our eighteenth LPP cycle ("LPP 18") to each of our NEOs, which are expected to be settled in 2026 contingent upon the Company's adjusted diluted earnings per share performance over the January 1, 2023 to December 31, 2025 performance period.

Annual Incentive Compensation. Annual incentives paid to our NEOs reflected our application of the incentive pool funding guidelines adopted by the Organization and Compensation Committee (the "Compensation Committee"), as well as the committee's evaluation of each NEO's contributions to our business and financial results, delivery of key strategic initiatives, and personal leadership qualities. The incentive pool funding guidelines included both a comparison of current year adjusted operating income results against the prior year and a People & Culture component, which assessed the Company's progress on inclusion and diversity objectives. Annual incentives for 2023 were awarded to our NEOs in early 2024 following the Company's achievement of adjusted operating income of $4,223 million. As part of the annual review process, Mr. Case proposed to the Compensation Committee that he and the other participants in the Senior Executive Incentive Compensation Plan receive annual incentives below the target amounts for fiscal 2023. Following their review of individual NEO performance and total incentive compensation outcomes, the Compensation Committee (and the independent members of the Board, in the case of Mr. Case) determined that each NEO receive 68% of his or her target annual incentive, other than Mr. Zeidel, who received an annual incentive of 96% of his target. For 2023, annual incentive awards to our NEOs were paid out entirely in PSUs, vesting on similar terms as LPP 19 awards, subject in addition to attainment of a share price hurdle, except that Mr. Zeidel received a portion ($250,000) of his earned annual incentive in cash.

• 2024 Aon Proxy Statement