EX-4.2





 Exhibit 4.2 

[FORM OF NOTE] 
 Unless this
Security is presented by an authorized representative of The Depository Trust Company (55 Water Street, New York, New York) to the issuer or its agent for registration of transfer, exchange or payment, and any Security issued upon registration of
transfer of, or in exchange for, or in lieu of, this Security is registered in the name of Cede & Co. or such other name as requested by an authorized representative of The Depository Trust Company and any payment hereon is made to
Cede & Co., ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL since the registered owner hereof, Cede & Co., has an interest herein. 

AON CORPORATION 
 2.800%
Senior Notes due 2030 
 Guaranteed by 

Aon plc 
 Aon plc 

Aon Global Holdings plc 
  

			
	 No.
	  	$        
	CUSIP No. 037389 BE2	  	 

 AON CORPORATION 

Aon Corporation, a Delaware corporation (herein called the “Company,” which term includes any successor Person under the
Indenture hereinafter referred to), for value received, hereby promises to pay to Cede & Co., as nominee for The Depository Trust Company, or registered assigns, the principal sum
of                ($                ) on May 15, 2030 and, subject to
Section 16.05 of said Indenture, to pay interest thereon from May 15, 2020 or from the most recent Interest Payment Date to which interest has been paid or duly provided for, semi-annually in arrears on each May 15 and
November 15, commencing November 15, 2020 (each, an “Interest Payment Date”), at the rate of 2.800% per annum, until the principal hereof is paid or made available for payment. The interest so payable, and punctually paid
or duly provided for, on any Interest Payment Date will, as provided in such Indenture, be paid to the Person in whose name this Security (or one or more predecessor Securities) is registered at the close of business on the Regular Record Date for
such interest, which shall be the May 1 or November 1 (whether or not a Business Day), as the case may be, immediately preceding such Interest Payment Date. Any such interest not so punctually paid or duly provided for will forthwith cease
to be payable to the Holder on such Regular Record Date and may either be paid to the Person in whose name this Security (or one or more predecessor Securities) is registered at the close of business on a subsequent record date for the payment of
such defaulted interest established by the Company, notice whereof shall be given to Holders of Securities of this series not less than 15 days prior to such subsequent record date, such record date to be not less than 5 days preceding the date of
payment of such defaulted interest, or be paid at any time in any other lawful manner not inconsistent with the requirements of any securities exchange on which the Securities of this series may be listed, and upon such notice as may be required by
such exchange, all as more fully provided in said Indenture. 












 Payment of the principal of (and premium, if any) and any such interest on this Security
will be made at the office or agency of the Company maintained for that purpose in the City of Chicago or the Borough of Manhattan, The City of New York, in such coin or currency of the United States of America as at the time of payment is legal
tender for payment of public and private debts; provided, however, that at the option of the Company payment of interest may be made by wire transfer, other electronic means or mailing checks to the address of the Holder entitled
thereto as such address shall appear in the Security Register. 
 The Securities of this series are subject to redemption and repurchase at
the option of the Company prior to the stated maturity as described in the Indenture and on the reverse hereof. 
 Reference is hereby made
to the further provisions of this Security set forth on the reverse hereof, which further provisions shall for all purposes have the same effect as if set forth at this place. 

Unless the certificate of authentication hereon has been executed by the Trustee referred to herein by manual or electronic signature, this
Security shall not be entitled to any benefit under the Indenture or be valid or obligatory for any purpose. 
 NOTICE TO HOLDER 

THE HOLDER OF THIS SECURITY IS HEREBY NOTIFIED, AND BY ITS ACCEPTANCE HEREOF ACKNOWLEDGES, THAT (1) THE COMPANY AND A GUARANTOR, IN
RESPECT OF ITS GUARANTEE, SHALL WITHHOLD OR DEDUCT FOR OR ON ACCOUNT OF ANY PRESENT OR FUTURE INCOME, STAMP OR OTHER TAX, DUTY, LEVY, IMPOST, ASSESSMENT OR OTHER GOVERNMENTAL CHARGE OF ANY NATURE WHATSOEVER IMPOSED OR LEVIED BY OR ON BEHALF OF THE
GOVERNMENT OF THE UNITED STATES OR BY ANY AUTHORITY OR AGENCY THEREIN OR THEREOF HAVING THE POWER TO TAX (COLLECTIVELY, “UNITED STATES TAXES”) AS REQUIRED BY LAW OF THE UNITED STATES AND (2) IF THE COMPANY OR A GUARANTOR (OR
WITHHOLDING AGENT FOR THE COMPANY OR GUARANTOR) IS SO REQUIRED TO WITHHOLD OR DEDUCT ANY AMOUNT FOR OR ON ACCOUNT OF UNITED STATES TAXES FROM ANY PAYMENT, NO ADDITIONAL AMOUNTS SHALL BE PAID TO A HOLDER OR BENEFICIAL OWNER FOR OR WITH RESPECT TO THE
AMOUNT SO WITHHELD OR DEDUCTED. 

  
 2 













 This is one of the Securities of the series designated therein referred to in the
within-mentioned Indenture. 
 Dated: May 15, 2020 
  

			
	AON CORPORATION, a corporation duly organized and existing under the laws of the State of Delaware
		
	By:	 	  

	Name:	 	Paul Hagy
	Title:	 	Senior Vice President and Treasurer


  

			
	Attest:
		
	By:	 	  

	Name:	 	Molly Johnson
	Title:	 	Vice President and Secretary

  

  
 [Signature Page to the
Note] 













 This is one of the Securities of the series designated therein referred to in the
within-mentioned Indenture. 
  

			
	 THE BANK OF NEW YORK MELLON
 TRUST
COMPANY, N.A., as Trustee

		
	By:	 	  

		 	Authorized Officer


 Dated: May 15, 2020 
  

  
 [Signature Page to the
Note] 













 This Security is one of a duly authorized series of securities of the Company entitled
“2.800% Senior Notes due 2030” (herein called the “Securities”) issued and to be issued in one or more series under the Indenture dated December 3, 2018, as supplemented by the Amended and Restated Indenture, dated
April 1, 2020, among the Company, the Guarantors and The Bank of New York Mellon Trust Company, N.A., as Trustee (herein called the “Trustee,” which term includes any successor trustee under the Indenture, as defined below) and
officers’ certificates dated May 15, 2020 (together, the “Indenture”), to which Indenture and all indentures supplemental thereto reference is hereby made for a statement of the respective rights, limitations of rights,
duties and immunities thereunder of the Company, the Trustee and the Holders of the Securities and of the terms upon which the Securities are, and are to be, authenticated and delivered. The Securities of this series will initially be issued in the
aggregate principal amount of $1,000,000,000. The Company may, from time to time, without the written consent of or notice to holders of the Securities of this series, create and issue under the Indenture additional securities having the same terms
and conditions as the Securities of this series (other than the issue date, the issue price and, to the extent applicable, the first date from which interest on such additional securities shall accrue and the first interest payment date for such
additional securities) and such additional securities shall be consolidated with and form a single series with the Securities of this series. 

At any time and from time to time prior to February 15, 2030 (such date, the “Par Call Date”), the Company may at its option
redeem all or some of the Securities of this series at a price equal to the greater of (1) 100% of the principal amount of the Securities to be redeemed and (2) the sum of the present values of the remaining scheduled payments of principal and
interest thereon (not including any portion of such payments of interest accrued as of the redemption date) from the redemption date to the Par Call Date, discounted to the date of redemption on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months), at a rate equal to the sum of the applicable Treasury Rate (as defined below), plus 35 basis points, plus, in each case,
accrued and unpaid interest thereon to but excluding the redemption date (each such redemption being an “Optional Redemption”). 

At any time and from time to time on or after the Par Call Date, the Company may at its option redeem all or some of the Securities at a
redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid interest thereon to but excluding the redemption date. 

If the Company has given notice of Optional Redemption as provided herein and in the Indenture and funds for the redemption of any Securities
of this series called for Optional Redemption have been made available on the applicable redemption date, such Securities will cease to bear interest on the date fixed for redemption. Thereafter, the only right of the Holders of such Securities will
be to receive payment of the applicable redemption price. 
 The Company will prepare and send a notice of an Optional Redemption to each
Holder of Securities to be redeemed by first-class mail at least 30 and not more than 90 calendar days prior to the date fixed for such Optional Redemption. On and after the 












 
redemption date for an Optional Redemption, interest will cease to accrue on the Securities called for redemption (unless the Company defaults in the payment of the redemption price). 

“Comparable Treasury Issue” means the U.S. Treasury security selected by the Quotation Agent as having a maturity comparable
to the remaining term of the Securities to be redeemed (assuming the Securities matured on the Par Call Date) that would be utilized, at the time of selection and in accordance with customary financial practice, in pricing new issues of corporate
debt securities of comparable maturity to the remaining term of the Securities (assuming the Securities matured on the Par Call Date). 

“Comparable Treasury Price” means, with respect to any redemption date, (i) the average of three Reference Treasury
Dealer Quotations for such redemption date, after excluding the highest and lowest such Reference Treasury Dealer Quotations, or (ii) if the Quotation Agent is given fewer than five such Reference Treasury Dealer Quotations, the average of all
such quotations, or (iii) if only one Reference Treasury Dealer Quotation is received, such quotation. 
 “Quotation
Agent” means the Reference Treasury Dealer appointed by the Company. 
 “Reference Treasury Dealer” means each of
Citigroup Global Markets Inc., Deutsche Bank Securities Inc. and Morgan Stanley & Co. LLC (or their respective affiliates that are primary U.S. government securities dealers in New York City, each of which the Company refers to as a
“Primary Treasury Dealer”) and their respective successors and two other nationally recognized investment banking firms that are Primary Treasury Dealers appointed from time to time by the Company; provided, however, that if any of the
foregoing shall cease to be a Primary Treasury Dealer, the Company will substitute therefor another Primary Treasury Dealer. 

“Reference Treasury Dealer Quotations” means, with respect to each Reference Treasury Dealer and any redemption date, the
average, as determined by the Quotation Agent, of the bid and asked prices for the Comparable Treasury Issue (expressed in each case as a percentage of its principal amount) quoted in writing to the Quotation Agent by such Reference Treasury Dealer
at 5:00 p.m., New York City time, on the third business day preceding such redemption date. 
 “Treasury Rate” means, with
respect to any redemption date, the rate per annum equal to the semi-annual equivalent yield to maturity of the Comparable Treasury Issue, assuming a price for the Comparable Treasury Issue (expressed as a percentage of its principal amount) equal
to the Comparable Treasury Price for such redemption date. 
 All payments made by a Guarantor with respect to its Guarantee shall be made
free and clear of and without withholding or deduction for or on account of any present or future income, stamp or other tax, duty, levy, impost, assessment or other governmental charge of any nature whatsoever imposed or levied by or on behalf of
the government of the United Kingdom or Ireland, as applicable, or, in each case, by any authority or agency therein or thereof having the power to tax (collectively, “Taxes”), unless such Guarantor is required to withhold or deduct
Taxes by law. 












 If an Event of Default with respect to the Securities of this series shall occur and be
continuing, the principal amount of and accrued and unpaid interest, if any, on the Securities of this series may be declared due and payable in the manner and with the effect provided in the Indenture. 

The Indenture contains provisions for defeasance at any time of the entire indebtedness of this Security or certain restrictive covenants and
Events of Default with respect to this Security, in each case upon compliance with certain conditions set forth therein. 
 The Indenture
permits, with certain exceptions as therein provided, the amendment thereof and the modification of the rights and obligations of the Company and the rights of the Holders of the Securities of each series to be affected under the Indenture at any
time by the Company and the Trustee with the consent of the Holders of a majority in principal amount of the Securities at the time Outstanding of each series to be affected. The Indenture also contains provisions permitting the Holders of specified
percentages in principal amount of the Securities of each series at the time Outstanding, on behalf of the Holders of all Securities of such series, to waive compliance by the Company with certain provisions of the Indenture and certain past
defaults under the Indenture and their consequences. Any such consent or waiver by the Holder of this Security shall be conclusive and binding upon such Holder and upon all future Holders of this Security and of any Security issued upon the
registration of transfer hereof or in exchange herefor or in lieu hereof, whether or not notation of such consent or waiver is made upon this Security. 

No reference herein to the Indenture and no provision of this Security or of the Indenture shall alter or impair the obligation of the
Company, which is absolute and unconditional, to pay the principal of and any premium and interest on this Security at the times, place and rate, and in the coin or currency, herein prescribed. 

As provided in the Indenture and subject to certain limitations therein set forth, the transfer of this Security is registerable in the
Security Register, upon surrender of this Security for registration of transfer at the office or agency of the Company in any place where the principal of and any premium and interest on this Security are payable, duly endorsed by, or accompanied by
a written instrument of transfer in form satisfactory to the Company and the Security Registrar duly executed by, the Holder hereof or his attorney duly authorized in writing, and thereupon one or more new Securities of this series and of like
tenor, of authorized denominations and for the same aggregate principal amount, will be issued to the designated transferee or transferees. 

The Securities of this series are issuable only in registered form without coupons in denominations of $2,000 and integral multiples of
$1,000. As provided in the Indenture and subject to certain limitations therein set forth, Securities of this series are exchangeable for a like aggregate principal amount of Securities of this series and of like tenor of a different authorized
denomination, as requested by the Holder surrendering the same. 












 No service charge shall be made for any such registration of transfer or exchange, but the
Company may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection therewith. 
 Prior to
due presentment of this Security for registration of transfer, the Company, the Trustee and any agent of the Company or the Trustee may treat the Person in whose name this Security is registered as the owner hereof for all purposes, whether or not
this Security be overdue, and neither the Company, the Trustee nor any such agent shall be affected by notice to the contrary. 
 Interest
on this Security shall be computed on the basis of a 360-day year consisting of twelve 30-day months. 

All terms used but not defined in this Security which are defined in the Indenture shall have the meanings assigned to them in the Indenture.

 This Security shall be governed by and construed in accordance with the laws of the State of New York without giving effect to the
conflict of laws provisions thereof. 












 ASSIGNMENT 

I or we assign and transfer this Security to: 
  

	
	                                   
                                         

	(Insert assignee’s social security or tax I.D. number)
	
	                                   
                                         

	(Print or type name, address and zip code of assignee)

 and irrevocably appoint: 
 as
agent to transfer this Security on the books of the Company. The agent may substitute another to act for him. 
  

							
	 Date:

                      
          
	  	 

                        
	  	 Your
 Signature:
	  	                                     
               
		  		  		  	 (Sign exactly as your name
 appears on the
face of this
 Security)


  

	
	 Signature

Guarantee:
                                         
                                   


 Signatures must be guaranteed by an “eligible guarantor institution” meeting the requirements of the
Security Registrar, which requirements include membership or participation in the Security Transfer Agent Medallion Program (“STAMP”) or such other “signature guarantee program” as may be determined by the Security
Registrar in addition to, or in substitution for, STAMP, all in accordance with the Securities Exchange Act of 1934, as amended. 












 NOTATION OF GUARANTEE 

For value received, the undersigned Guarantor (which term includes any successor Person under the Indenture), subject to the provisions in the
Indenture and the terms of the Securities of this series, has fully, unconditionally and irrevocably guaranteed to and for the benefit of each Holder and the Trustee the due and prompt payment in full of all amounts which may at any time be or
become from time to time due and payable by the Company under the Indenture or otherwise with respect to the Securities of this series registered in such Holder’s name, at their stated due dates or when otherwise due in accordance with the
terms thereof. The obligations of the Guarantor to the Holders of Securities and to the Trustee pursuant to the Guarantee under the Indenture are expressly set forth in Article Fifteen of the Indenture and reference is hereby made to the Indenture
for the precise terms of the Guarantee. Each Holder of a Security, by accepting the same, (a) agrees to and shall be bound by such provisions and (b) appoints the Trustee
attorney-in-fact of such Holder for the purpose of such provisions. 
  

			
	Aon plc, a public limited company duly organized and existing under the laws of Ireland
		
	By:	 	  

	Name:	 	Paul Hagy
	Title:	 	Senior Vice President and Treasurer


  

  
 [Guarantor Signature
Page to the Note] 













 NOTATION OF GUARANTEE 

For value received, the undersigned Guarantor (which term includes any successor Person under the Indenture), subject to the provisions in the
Indenture and the terms of the Securities of this series, has fully, unconditionally and irrevocably guaranteed to and for the benefit of each Holder and the Trustee the due and prompt payment in full of all amounts which may at any time be or
become from time to time due and payable by the Company under the Indenture or otherwise with respect to the Securities of this series registered in such Holder’s name, at their stated due dates or when otherwise due in accordance with the
terms thereof. The obligations of the Guarantor to the Holders of Securities and to the Trustee pursuant to the Guarantee under the Indenture are expressly set forth in Article Fifteen of the Indenture and reference is hereby made to the Indenture
for the precise terms of the Guarantee. Each Holder of a Security, by accepting the same, (a) agrees to and shall be bound by such provisions and (b) appoints the Trustee
attorney-in-fact of such Holder for the purpose of such provisions. 
  

			
	Aon plc, a public limited company duly organized and existing under the laws of England Wales
		
	By:	 	  

	Name:	 	Paul Hagy
	Title:	 	Senior Vice President and Treasurer


  

  
 [Guarantor Signature
Page to the Note] 













 NOTATION OF GUARANTEE 

For value received, the undersigned Guarantor (which term includes any successor Person under the Indenture), subject to the provisions in the
Indenture and the terms of the Securities of this series, has fully, unconditionally and irrevocably guaranteed to and for the benefit of each Holder and the Trustee the due and prompt payment in full of all amounts which may at any time be or
become from time to time due and payable by the Company under the Indenture or otherwise with respect to the Securities of this series registered in such Holder’s name, at their stated due dates or when otherwise due in accordance with the
terms thereof. The obligations of the Guarantor to the Holders of Securities and to the Trustee pursuant to the Guarantee under the Indenture are expressly set forth in Article Fifteen of the Indenture and reference is hereby made to the Indenture
for the precise terms of the Guarantee. Each Holder of a Security, by accepting the same, (a) agrees to and shall be bound by such provisions and (b) appoints the Trustee
attorney-in-fact of such Holder for the purpose of such provisions. 
  

			
	Aon Global Holdings plc, a public limited company duly organized and existing under the laws of England Wales
		
	By:	 	  

	Name:	 	Domingo Garcia
	Title:	 	Director


  

  
 [Guarantor Signature
Page to the Note]