EX-23 4 a2207295zex-23.htm EX-23
QuickLinks -- Click here to rapidly navigate through this document


Exhibit 23


CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

        We consent to the incorporation by reference in the following Registration Statements:

Registration Statement    
Form   Number   Purpose
 

S-8

    33-27984  

Pertaining to Aon's savings plan


 


S-8


 

 


33-42575

 


Pertaining to Aon's stock award plan and stock option plan


 


S-8


 

 


33-59037

 


Pertaining to Aon's stock award plan and stock option plan


 


S-3


 

 


333-50607

 


Pertaining to the registration of 369,000 shares of common stock


 


S-8


 

 


333-55773

 


Pertaining to Aon's stock award plan, stock option plan, and employee stock purchase plan


 


S-3


 

 


333-78723

 


Pertaining to the registration of debt securities, preferred stock and common stock


 


S-4


 

 


333-168320

 


Pertaining to the registration of 4,545,566 shares of common stock registered on Post Effective Amendment No. 1


 


S-4


 

 


333-57706

 


Pertaining to the registration of up to 3,852,184 shares of common stock


 


S-3


 

 


333-100466

 


Pertaining to the registration as amended of 2,707,018 shares of common stock


 


S-8


 

 


333-103344

 


Pertaining to the registration of common stock


 


S-8


 

 


333-106584

 


Pertaining to Aon's deferred compensation plan


 


S-8


 

 


333-145928

 


Pertaining to the registration of common stock


 


S-8


 

 


333-145930

 


Pertaining to the registration of common stock underlying equity securities issued to Aon's president and chief executive officer


 


S-3


 

 


333-159841

 


Pertaining to the registration of debt securities, preferred stock, common stock, convertible securities, share purchase contracts, share purchase units and guarantees


 


S-8


 

 


333-174788

 


Pertaining to Aon's 2011 stock incentive plan and 2011 employee stock purchase plan


 


S-8


 

 


333-178906

 


Pertaining to Aon's savings plan


 


S-4


 

 


333-178991

 


Pertaining to the registration of 355,110,708 Class A Ordinary Shares of Aon Global Limited, and in the related Proxy Statement / Prospectus of Aon Global and Aon Corporation contained therein

of our reports dated February 24, 2012, with respect to the consolidated financial statements of Aon Corporation and the effectiveness of internal control over financial reporting of Aon Corporation, included in this Annual Report (Form 10-K) for the year ended December 31, 2011.

/s/ ERNST & YOUNG LLP

Chicago, Illinois
February 24, 2012




QuickLinks

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM