Sec Form 4 Filing - CONCANNON CHRISTOPHER R @ MARKETAXESS HOLDINGS INC - 2023-04-03

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 CONCANNON CHRISTOPHER R 2. Issuer Name and Ticker or Trading Symbol MARKETAXESS HOLDINGS INC [ MKTX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Executive Officer (Last) (First) (Middle) C/O MARKETAXESS HOLDINGS INC., 55 HUDSON YARDS, 15TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 04/03/2023 (Street) NEW YORK, NY10001 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, par value $0.003 per share 04/03/2023 A 2,729 A $ 0 ( 1 ) 42,896 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 Performance Stock Units ( 2 ) 04/03/2023 A 5,039 ( 2 ) ( 2 ) Common Stoc k 5,039 $ 0 5,039 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other CONCANNON CHRISTOPHER R C/O MARKETAXESS HOLDINGS INC. 55 HUDSON YARDS, 15TH FLOOR NEW YORK, NY10001 X Chief Executive Officer Signatures /s/ Jason Edelstein, as Attorney-in-Fact for Christopher R. Concannon 04/05/2023 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents a grant of restricted stock units pursuant to the Company's 2020 Equity Incentive Plan (the "Plan"). Subject to the terms of the Plan and the Restricted Stock Unit Agreement, the restricted stock units will vest in three installments of 25% on April 3, 2026, 25% on April 3, 2027 and 50% on April 3, 2028. ( 2 )Each performance stock unit ("PSU") granted pursuant to the Plan represents a contingent right to receive one share of the Company's common stock. 1,260 PSUs shall have a three-year performance period; 1,260 PSUs shall have a four-year performance period; and 2,519 PSUs shall have a five-year performance period. Subject to the terms of the Plan and the Performance Stock Unit Agreement, the PSUs will vest and shares of common stock shall be awarded for each performance period based upon achievement, as determined by the Company's Compensation Committee, of a compound annual growth rate performance metric, calculated using (i) a starting stock price equal to the average closing stock price of each trading day during the thirty (30) calendar days immediately preceding the Grant Date and (ii) an ending stock price equal to the average closing stock price of each trading day during the ninety (90) calendar days ending on the final day of the applicable Performance Period.

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

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