Sec Form 3/A Filing - Refinitiv US PME LLC @ Tradeweb Markets Inc. - 2023-12-31

FORM 3/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 Refinitiv US PME LLC 2. Issuer Name and Ticker or Trading Symbol Tradeweb Markets Inc. [ TW] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 28 LIBERTY PLACE, 58TH FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 12/31/2023 (Street) NEW YORK, NY10005 4. If Amendment, Date Original Filed (MM/DD/YY) 02/08/2021 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 Class C Common Stock ( 2 ) 18,000,000 D ( 5 ) ( 6 ) ( 7 ) ( 8 ) ( 9 ) ( 10 ) ( 11 )

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 Class B Common Stock ( 1 ) ( 1 ) ( 1 ) Class A Common Stock 96,933,192 I See Footnotes ( 4 ) ( 6 ) ( 7 ) ( 8 ) ( 9 ) ( 10 ) ( 11 ) Class D Common Stock ( 2 ) ( 3 ) ( 2 )( 3 ) ( 2 )( 3 ) Class C Common Stock 4,988,329 I See Footnotes ( 5 ) ( 6 ) ( 7 ) ( 8 ) ( 9 ) ( 10 ) ( 11 ) Non-voting common units of Tradeweb Markets LLC ( 3 ) ( 3 ) ( 3 ) Class A Common Stock ( 2 ) ( 3 ) 22,988,329 I See Footnotes ( 5 ) ( 6 ) ( 7 ) ( 8 ) ( 9 ) ( 10 ) ( 11 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Refinitiv US PME LLC 28 LIBERTY PLACE, 58TH FLOOR NEW YORK, NY10005 X Refinitiv US LLC 28 LIBERTY PLACE, 58TH FLOOR NEW YORK, NY10005 X LSEGA, Inc. 28 LIBERTY PLACE, 58TH FLOOR NEW YORK, NY10005 X LSEG US Holdco, Inc. 28 LIBERTY PLACE, 58TH FLOOR NEW YORK, NY10005 X Refinitiv TW Holdings Ltd. FIVE CANADA SQUARE, CANARY WHARF LONDON, X0E14 5AQ X Refinitiv Parent Ltd FIVE CANADA SQUARE, CANARY WHARF LONDON, X0E14 5AQ X London Stock Exchange Group plc 10 PATERNOSTER SQUARE LONDON, X0EC4M 7LS X Signatures /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for REFINITIV US PME LLC 01/03/2024 Signature of Reporting Person Date /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for REFINITIV US LLC 01/03/2024 Signature of Reporting Person Date /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for LSEGA, INC. 01/03/2024 Signature of Reporting Person Date /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for LSEG US HOLDCO, INC. 01/03/2024 Signature of Reporting Person Date /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for REFINITIV TW HOLDINGS LTD. 01/03/2024 Signature of Reporting Person Date /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for REFINITIV PARENT LIMITED 01/03/2024 Signature of Reporting Person Date /s/ Teresa Hogan Teresa Hogan, attorney-in-fact for LONDON STOCK EXCHANGE GROUP PLC 01/03/2024 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares of the Issuer's Class B common stock ("Class B Common Stock") have ten votes per share and are exchangeable for shares of the Issuer's Class A common stock ("Class A Common Stock") on a one-for-one basis at the discretion of the holder. These exchange rights do not expire. ( 2 )Shares of Class D common stock of the Issuer ("Class D Common Stock") have ten votes per share but no economic rights (including rights to dividends or, other than their par value, distributions upon liquidation) and are issued in an equal amount to the number of non-voting common units of Tradeweb Markets LLC, a subsidiary of the Issuer ("LLC Units"), held. Shares of Class D Common Stock are exchangeable for shares of the Issuer's Class C common stock ("Class C Common Stock"), which have one vote per share but no economic rights (other than their par value upon liquidation), on a one-for-one basis at the discretion of the holder. These exchange rights do not expire. On December 29, 2023, Refinitiv US PME LLC elected to exchange 18,000,000 shares of Class D Common Stock for 18,000,000 shares of Class C Common Stock. ( 3 )Pursuant to the terms of the limited liability company agreement for Tradeweb Markets LLC, LLC Units may be exchanged for shares of Class A Common Stock or Class B Common Stock, in each case, on a one-for-one basis at the discretion of the holder. Upon such an exchange, a corresponding number of shares of Class D Common Stock (or shares of Class C Common Stock, in the event the holder exchanged its shares of Class D Common Stock as described above) will be canceled. These exchange rights do not expire. ( 4 )These securities are directly held by Refinitiv TW Holdings Ltd. ( 5 )These securities are directly held by Refinitiv US PME LLC. ( 6 )Refinitiv US LLC is the controlling member of Refinitiv US PME LLC. LSEGA, Inc. is the sole member of Refinitiv US LLC. Refinitiv Parent Limited is the sole shareholder of LSEG US Holdco, Inc., which is the sole shareholder of LSEGA, Inc. IAG US LLC is a member of Refinitiv US PME LLC. Refinitiv International Holdings S.a r.l. is the sole member of IAG US LLC. Refinitiv Netherlands Holdings BV is the sole shareholder of Refinitiv International Holdings S.a r.l. ( 7 )Refinitiv UK (Rest of World) Holdings Limited is the sole shareholder of Refinitiv Netherlands Holdings BV. Refinitiv UK Parent Limited is the sole shareholder of Refinitiv UK (Rest of World) Holdings Limited. LSEGA Jersey Limited is the sole shareholder of Refinitiv UK Parent Limited. Refinitiv Parent Limited is the sole shareholder of LSEGA Jersey Limited. London Stock Exchange Group plc is the controlling shareholder of Refinitiv Parent Limited. LSEGA Limited and LSEGA2 Limited are shareholders of Refinitiv Parent Limited and London Stock Exchange Group plc is the sole shareholder of each of LSEGA Limited and LSEGA2 Limited. ( 8 )Information with respect to each of the Reporting Persons is given solely by such Reporting Person, and no Reporting Person has responsibility for the accuracy or completeness of information supplied by another Reporting Person. ( 9 )Pursuant to the terms of a stock purchase agreement (the "Stock Purchase Agreement") entered into by, among others, London Stock Exchange Group plc ("LSEG") and Refinitiv Holdings Limited ("Refinitiv Holdings") originally entered into on August 1, 2019, amended on August 23, 2019, and amended and restated on November 4, 2019, LSEG (directly and through certain wholly owned subsidiaries) acquired the entire issued and to be issued share capital of Refinitiv Parent Limited ("Refinitiv Parent") from the Refinitiv Sellers (consisting of certain subsidiaries of Refinitiv Holdings) and, in exchange, LSEG will issue 204,225,968 consideration shares (the "Consideration Shares"), such Consideration Shares comprised of: (i) LSEG ordinary shares; and (ii) LSEG limited-voting ordinary shares. ( 10 )As a result of its acquisition of the share capital of Refinitiv Parent, LSEG acquired 96,933,192 shares of Class B Common Stock, 22,988,329 LLC Units and 22,988,329 shares of Class D Common Stock. The transaction closed on January 29, 2021 (the "Closing"). Of the total number of Consideration Shares expected to be issued, 179,610,123 LSEG shares were issued to the Refinitiv Sellers at Closing. In addition, 24,615,845 LSEG ordinary shares were issued on March 1, 2021 to ConsortiumCo, a company owned by affiliates of Blackstone (the "Deferred Issue Shares"). The issue of the Deferred Issue Shares to ConsortiumCo was in connection with the settlement of certain existing payment-in-kind shares in Refinitiv Holdings' capital structure. ( 11 )Each of the Reporting Persons (other than to the extent it directly holds securities reported herein) disclaims beneficial ownership of the securities held by the other Reporting Persons, except to the extent of such Reporting Person's pecuniary interest therein, and, pursuant to Rule 16a-1(a)(4) under the Securities Exchange Act of 1934, each of the Reporting Persons (other than to the extent it directly holds securities reported herein) states that the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of all of the reported securities for purposes of Section 16 or for any other purpose.

Remarks: This Form 3/A amends the Form 3 filed on behalf of Refinitiv US PME LLC, Refinitiv US LLC, LSEGA, Inc., Refinitiv TW Holdings Ltd., Refinitiv Parent Limited and London Stock Exchange Group plc on February 8, 2021 to reflect that, as a result of an intragroup reorganization, LSEG US Holdco, Inc. became the sole shareholder of LSEGA, Inc. LSEG US Holdco, Inc. is a wholly-owned subsidiary of Refinitiv Parent Limited. Exhibit 24.1 - Power of Attorney for Reporting Persons (other than LSEG US Holdco, Inc.) Exhibit 24.2 - Power of Attorney for LSEG US Holdco, Inc.

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