Sec Form 4 Filing - WESTPHAL MARK W @ Post Holdings, Inc. - 2022-03-29

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person WESTPHAL MARK W 2. Issuer Name and Ticker or Trading Symbol Post Holdings, Inc. [ POST] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) PRES., FOODSERVICE (Last) (First) (Middle) C/O POST HOLDINGS, INC., 2503 S. HANLEY ROAD 3. Date of Earliest Transaction (MM/DD/YY) 03/29/2022 (Street) ST. LOUIS, MO63144 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 03/29/2022 A 10,557( 1 )( 2 ) A $ 0 81,507( 3 ) D Common Stock 16,253.889 I By 401(k) Plan

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Employee Stock Options (right to buy) $ 53.63( 4 ) 03/10/2022 A V 9,901( 4 ) ( 5 ) 12/01/2027 Common Stock 9,901 $ 0 30,409 D Employee Stock Options (right to buy) $ 62.1( 4 ) 03/10/2022 A V 11,170( 4 ) ( 5 ) 11/13/2028 Common Stock 11,170 $ 0 34,306 D Restricted Stock Units ( 6 ) 03/10/2022 A V 5,887( 7 ) ( 8 ) 11/16/2031 Common Stock 5,887 $ 0 18,080 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other WESTPHAL MARK W C/O POST HOLDINGS, INC. 2503 S. HANLEY ROAD ST. LOUIS, MO63144 PRES., FOODSERVICE Signatures /s/ Diedre J. Gray, Attorney-in-Fact 03/31/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )In connection with the spin-off of BellRing Brands, Inc. by Post Holdings, Inc. ("Post"), which closed on March 10, 2022 (the "Spin-Off"), performance-based restricted stock units with a total shareholder return performance metric granted in 2019 (the "2019 PRSUs") and outstanding as of immediately prior to the Spin-Off were converted into time-based restricted stock units, with the number of shares subject to such time-based restricted stock units determined based on Post's achievement of Post's Relative TSR Percentile Rank (as such term is defined in the award agreement for the grant of the 2019 PRSUs (the "Award Agreement"); provided, that the Ending Stock Price (as such term is defined in the Award Agreement) was determined based on the average of the closing sale prices for a share of common stock of the applicable company for the 250 trading days immediately preceding and including March 10, 2022. ( 2 )The restricted stock units will vest in full on October 15, 2022 (subject to the Reporting Person's continued employment through such date). An adjustment was also made to the number of converted time-based restricted stock units by providing additional Post restricted stock units to the Reporting Person in order to reflect the impact of the Spin-Off. ( 3 )In connection with the Spin-Off, and in accordance with their terms, adjustments were made to outstanding restricted stock unit awards by providing additional Post restricted stock units to the Reporting Person in order to reflect the impact of the Spin-Off. ( 4 )In connection with the Spin-Off and in accordance with its terms, adjustments were made to outstanding stock option awards by increasing the number of stock options and reducing the exercise price in order to reflect the impact of the Spin-Off. ( 5 )Options are fully vested. ( 6 )Each restricted stock unit represents a contingent right to receive one share of Post's common stock. The restricted stock units were granted under the Post Holdings, Inc. 2021 Long-Term Incentive Plan in a transaction exempt under Rule 16b-3 on November 16, 2021. ( 7 )Represents an adjustment to the outstanding restricted stock units to reflect the impact of the Spin-Off. ( 8 )One-third of the restricted stock units vest on each of the first, second, and third anniversaries of the date of grant without any action on the part of the participant.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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