EX-4.3





 Exhibit 4.3 

AMEREN CORPORATION 

Company Order 

March 5, 2021 
 The Bank of
New York Mellon Trust Company, N.A., 
 as Trustee 
 2 North
LaSalle Street, Suite 700 
 Chicago, Illinois 60602 
  

	 	Re:	 1.75% Senior Notes due 2028 



Ladies and Gentlemen: 
 Application is hereby
made to The Bank of New York Mellon Trust Company, N.A., a national banking association, as successor trustee (the “Trustee”), under the Indenture, dated as of December 1, 2001, as amended and supplemented (the
“Indenture”), between Ameren Corporation, a Missouri corporation (the “Company”), and the Trustee for the authentication and delivery of $450,000,000 aggregate principal amount of the Company’s 1.75% Senior
Notes due 2028 (the “Notes”), pursuant to the provisions of Article II of the Indenture. The Company, at any time and from time to time, without the consent of the holders of the Notes, may deliver additional Notes of the same
series executed by the Company to the Trustee for authentication, having the same terms and conditions (including the same CUSIP number) as the Notes authenticated pursuant hereto in all respects, except for the date of original issuance, the
offering price, and, if applicable, the initial interest accrual date and the initial interest payment date. Such additional Notes shall be part of the same series as the Notes authenticated pursuant hereto. All capitalized terms not defined herein
that are defined in the Indenture shall have the same meaning as used in the Indenture. 
 The Notes will be issued in the form of a Global
Note registered in the name of Cede & Co. (as nominee for The Depository Trust Company (“DTC”), New York, New York, which will act as the Depositary for the Global Note). Pursuant to Section 2.05(c) of the Indenture,
the Notes will have the terms set forth in the form of Global Note attached hereto as Exhibit A (which terms are incorporated by reference in this Company Order). The Global Note shall bear the depositary legend in
substantially the form set forth in Exhibit A attached hereto. The Notes will be issued only in denominations of $2,000 and in integral multiples of $1,000 in excess thereof. 

In connection with this Company Order, there are delivered to you herewith the following: 

 

	 	1.	 Certified copies of the resolutions adopted by the Finance Committee of the Board of Directors of the Company
authorizing this Company Order and the issuance and sale of the Notes by the Company pursuant to Section 2.05(c)(1) of the Indenture; 















	 	2.	 Opinions of Counsel addressed to you or in which it is stated that you may rely pursuant to Sections 2.05(c)(2)
and 15.05 of the Indenture; 


  

	 	3.	 Officers’ Certificate pursuant to Sections 2.05(c)(3) and 15.05 of the Indenture; and



  

	 	4.	 Global Note (No. R-1) representing the Notes executed on behalf of the
Company in accordance with the terms of Section 2.05(a) of the Indenture, specifying the terms of the Notes (which terms are incorporated by reference herein). 



The Global Note representing the Notes is to be held for delivery through the facilities of DTC to Barclays Capital Inc. on behalf of the several underwriters
thereof, against payment therefor at the closing in respect of the sale thereof, such closing to be held at 10:00 a.m., New York time, March 5, 2021, at the offices of Morgan, Lewis & Bockius LLP, 101 Park Avenue, New York, New
York 10178. You are hereby instructed to authenticate the Global Note representing the Notes in the name of Cede & Co. as registered holder and to hold it as custodian for DTC. 












 Please acknowledge receipt of the Global Note representing the Notes, the instructions
referred to above and the supporting documentation pursuant to the Indenture referred to above. 
  

					
	Very truly yours,
	
	AMEREN CORPORATION
		
	By:	 	 /s/ Darryl T. Sagel

		 	Name:	 	Darryl T. Sagel
		 	Title:	 	Vice President and Treasurer



  
 Company Signature Page
to Company Order 













 Receipt from the Company of the Global Note representing the Notes, the instructions
referred to above and the supporting documentation pursuant to the Indenture in connection with the authentication and delivery of the Notes is hereby acknowledged. 

 

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

as Trustee

		
	By:	 	 /s/ Mark A. Golder

		 	Name:	 	Mark A. Golder
		 	Title:	 	Vice President



  
 Trustee Signature Page
to Company Order