AON Aon PLC

Filed pursuant to Rule 433

Relating to Preliminary Prospectus Supplement dated February 23, 2022 to

Prospectus dated May 12, 2020

Registration Statement Nos. 333-238189, 333-238189-01, 333-238189-02 and 333-238189-03

Aon Corporation and Aon Global Holdings plc

$600,000,000 2.850% SENIOR NOTES DUE 2027 (the “2027 Notes”)

$900,000,000 3.900% SENIOR NOTES DUE 2052 (the “2052 Notes”)

(together, the “Notes”)

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*Note: An explanation of the significance of ratings may be obtained from the rating agencies. Generally, rating agencies base their ratings on such material and information, and such of their own investigations, studies and assumptions, as they deem appropriate. The rating of the Notes should be evaluated independently from similar ratings of other securities. A credit rating of a security is not a recommendation to buy, sell or hold securities and may be subject to review, revision, suspension, reduction or withdrawal at any time by the assigning rating agency.

**Note: Under Rule 15c6-1 under the Securities Exchange Act of 1934, as amended, trades in the secondary market generally are required to settle in two business days, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the Notes offered hereby on the date of pricing will be required, by virtue of the fact that such Notes initially will settle T+3, to specify an alternate settlement cycle at the time of any such trade to prevent a failed settlement. Purchasers of these Notes who wish to trade the Notes on the date of pricing should consult their own advisors.

The issuers and the guarantors have filed a registration statement, including a prospectus, with the SEC for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuers have filed with the SEC for more complete information about the issuers, the guarantors and this offering. You may get these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, the Joint Book-Running Managers in the offering will arrange to send you the prospectus if you request it by contacting Morgan Stanley & Co. LLC at 1-866-718-1649, Barclays Capital Inc. at 1-888-603-5847, Credit Suisse Securities (USA) LLC at 1-800-221-1037 or Deutsche Bank Securities Inc. 1-800-503-4611.

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