Sec Form 4/A Filing - Rayner Craig R. @ Certara, Inc. - 2021-04-01

FORM 4/A 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 Rayner Craig R. 2. Issuer Name and Ticker or Trading Symbol Certara, Inc. [ CERT] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) PRESIDENT, INTEGRATED DRUG DEV (Last) (First) (Middle) C/O CERTARA, INC., 100 OVERLOOK CENTER, SUITE 101 3. Date of Earliest Transaction (MM/DD/YY) 04/01/2021 (Street) PRINCETON, NJ08540 4. If Amendment, Date Original Filed (MM/DD/YY) 04/09/2021 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 04/01/2021 A 38,462 ( 1 ) A $ 0 479,396 D

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Rayne r Craig R. C/O CERTARA, INC. 100 OVERLOOK CENTER, SUITE 101 PRINCETON, NJ08540 PRESIDENT, INTEGRATED DRUG DEV Signatures /s/ Richard M. Traynor, Attorney-in Fact for Craig R. Rayner 06/15/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The original Form 4, filed on April 9, 2021, is being amended by this Form 4 amendment solely to correct an administrative error, which misreported the number of restricted stock units granted on April 1, 2021 as a total of 23,810 restricted stock units being issued when in fact, 38,462 restricted stock units were issued. As a result of this administrative error, the number of shares beneficially owned by the reporting person following the corrected transaction reflects an increase in the number of shares as beneficially owned by the reporting person by 14,652 shares. All 38,462 restricted stock units received by the reporting person will vest, and the underlying shares of the issuer's common stock will be concurrently issued in a series of three equal installments upon the reporting person's completion of each 12 month period of service over the period measured from April 1, 2021 to April 1, 2024, subject to the continued service of the reporting person through such vesting dates.

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).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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