Issuer:

Aon plc

Securities:

4.750% Senior Notes due 2045

Guarantor:

Aon Corporation

Legal Format:

SEC Registered

Amount:

$600,000,000

Ranking:

Senior Unsecured

Expected Ratings(1):

Moody’s Investors Service: Baa2

Standard & Poor’s: A-

Fitch: BBB+

Trade Date:

May 13, 2015

Settlement Date (T+5):

May 20, 2015

Maturity Date:

May 15, 2045

Reference Treasury:

3.00% due November 15, 2044

Reference Treasury Yield and Price:

3.070% or 98-20+

Reoffer Spread to Treasury:

170 bps

Reoffer Yield:

4.770%

Coupon:

4.750%

Denominations:

$2,000 and multiples of $1,000

Interest Payment Dates:

Semi-annually in arrears on May 15 and November 15, beginning on November 15, 2015

Price to Public:

99.683%

Proceeds to Issuer:

$592,848,000

CUSIP / ISIN:

00185AAH7 / US00185AAH77

Optional Redemption:

We may redeem all of the Notes at any time or some of the Notes from time to time at a redemption price equal to the greater of 100% of the principal amount of the Notes being redeemed and a make whole using a discount rate of the Reference Treasury plus 30 basis points.

On or after November 15, 2044, we may redeem any or all of the Notes at a redemption price equal to 100% of the principal amount of the Notes being redeemed.

In the event of certain changes in respect of taxes applicable to the Notes or the Guarantee of the Notes, we may redeem the Notes in whole at any time at a redemption price equal to 100% of the principal amount of the Notes being redeemed.

See “Description of the Securities—Optional Redemption” and “Description of the Securities—Optional Tax Redemption” in the preliminary prospectus supplement for more information.

Joint Book-Running Managers:

Morgan Stanley & Co. LLC

Barclays Capital Inc.

HSBC Securities (USA) Inc.

J.P. Morgan Securities LLC

Co-Managers:

ANZ Securities, Inc.

Aon Benfield Securities, Inc.

BNY Mellon Capital Markets, LLC

Scotia Capital (USA) Inc.

Loop Capital Markets LLC

The Williams Capital Group, L.P.

Conflicts:

We intend to use the net proceeds of this offering for general corporate purposes which, among other things, may include repayment of all or part of our 3.50% senior notes due September 2015 (the ‘‘2015 Notes’’). As of March 31, 2015, $600 million of our 2015 Notes was outstanding. Certain of the underwriters or their affiliates may hold the 2015 Notes and, accordingly, may receive proceeds from this offering. To the extent that any one underwriter, together with its affiliates, receives more than 5% of the net proceeds such underwriter would be deemed to have a ‘‘conflict of interest’’ with us in regard to this offering under the requirements of Rule 5121 of the Financial Institution Regulatory Authority (“FINRA”).

In addition, Aon Benfield Securities, Inc. is an indirect wholly owned subsidiary of Aon plc.

Accordingly, this offering will be made in compliance with the applicable provisions of FINRA Rule 5121.