Sec Form 4 Filing - Moskowitz Paul G @ Waystar Holding Corp. - 2025-02-24

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 Moskowitz Paul G 2. Issuer Name and Ticker or Trading Symbol Waystar Holding Corp. [ WAY] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O BAIN CAPITAL PRIVATE EQUITY, LP, 200 CLARENDON STREET 3. Date of Earliest Transaction (MM/DD/YY) 02/24/2025 (Street) BOSTON, MA02116 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 $0.01 per share 02/24/2025 S( 3 ) 5,652,689 D $ 38.6 ( 3 ) 22,327,728 I See Footnote ( 1 ) ( 2 ) Common Stock, par value $0.01 per share 02/24/2025 J( 4 ) 573,192 D 21,754,536 I See Footnote ( 1 ) ( 2 )

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 Moskowitz Paul G C/O BAIN CAPITAL PRIVATE EQUITY, LP 200 CLARENDON STREET BOSTON, MA02116 X X Signatures /s/ Paul Moskowitz 02/26/2025 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Represents shares held by BCPE Derby Investor, LP ("Derby Investor") and BCPE Derby (DE) SPV, LP ("Derby SPV Investor"). Bain Capital Investors, LLC ("BCI") is the manager of Bain Capital Partners XI, L.P. ("Partners XI"), which is the general partner of Bain Capital Fund XI, L.P. ("Fund XI"). Fund XI is the (i) sole member of BCPE Derby GP, LLC ("Derby GP"), which is the general partner of Derby Investor and (ii) sole member of BCPE Derby (DE) SPV, LLC ("Derby SPV GP"), which is the general partner of Derby SPV Investor and, together with BCI, Partners XI, Fund XI, Derby GP, Derby Investor and Derby SPV GP, the "Bain Capital Entities"). ( 2 )(Continued from footnote 1) Paul G Moskowitz, a member of the board of directors of Waystar Holding Corp. (the "Issuer"), is a Partner of BCI. By virtue of the relationships described in this footnote, Mr. Moskowitz may be deemed to share voting and dispositive power with respect to the shares of the Issuer's common stock, par value $0.01 per share (the "Common Stock"), held by the Bain Capital Entities. Mr. Moskowitz disclaims beneficial ownership of such securities except to the extent of his pecuniary interest therein. ( 3 )Pursuant to a registered public offering that closed on February 24, 2025, 552,696 shares of Common Stock were sold by Derby Investor and 5,099,993 shares of Common Stock were sold by Derby SPV Investor at a price of $38.60 (net of underwriting discount). ( 4 )On February 24, 2025, Derby Investor distributed 347,013 shares of Common Stock and Derby SPV Investor distributed 226,179 shares of Common Stock to one or more of their respective members or partners in connection with certain charitable gifts made by such members or partners or their direct or indirect owners.

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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