Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

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

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(Print or Type Responses)

1. Name and Address of Reporting Person * Derby LuxCo S.a r.l. 2. Issuer Name and Ticker or Trading Symbol Waystar Holding Corp. [WAY] 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) 51A, BOULEVARD ROYAL,, LUXEMBOURG 3. Date of Earliest Transaction (Month/Day/Year) 09/12/2025 (Street) GRAND DUCHY OF LUXEMBOURG, N4 2449 4. If Amendment, Date Original Filed (Month/Day/Year) 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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 09/12/2025 S 7,766,088 D $39.21(1) 24,879,437 I Held directly by Derby LuxCo(2)

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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 (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

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 (Month/Day/Year)

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
Derby LuxCo S.a r.l. 51A, BOULEVARD ROYAL, LUXEMBOURG GRAND DUCHY OF LUXEMBOURG, N4 2449		X
EQT Fund Management S.a r.l. 51A, BOULEVARD ROYAL, LUXEMBOURG GRAND DUCHY OF LUXEMBOURG, N4 2449		X

Signatures

Derby LuxCo S.a r.l., By: /s/ Sanjay Fullee, Name: Sanjay Fullee, Title: Manager and /s/ Tinatin Gogoladze, Name: Tinatin Gogoladze, Title: Manager		09/16/2025
**Signature of Reporting Person		Date
EQT Fund Management S.a r.l., By: /s/ Sara Huda, Name: Sara Huda, Title: Manager and /s/ Christiaan Snyders, Name: Christiaan Snyders, Title: Authorized Signatory		09/16/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	This amount represents the $39.21 sale price per share of Common Stock, par value $0.01 per share, in a secondary offering, which closed on September 12, 2025.
(2)	Consists of shares of common stock held directly by Derby LuxCo S.a r.l. ("Derby LuxCo"). Several investment vehicles collectively make up the fund known as "EQT VIII." EQT VIII owns 100% of the membership interests in Derby LuxCo. EQT Fund Management S.a r.l. ("EFMS") has exclusive responsibility for the management and control of the business and affairs of investment vehicles which constitute the majority of the total commitments to EQT VIII. EFMS is overseen by a board of not less than three individuals that acts by majority approval.
Remarks: This filing shall not be deemed an admission that the Reporting Persons are beneficial owners of all securities covered by this filing for purposes of Section 16 of the Exchange Act or otherwise, and each Reporting Person disclaims beneficial ownership of these securities, except to the extent of such Reporting Person's pecuniary interest therein, if any.

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