WAY

SEC source: 0001998251-25-000004 · wk-form4a_1756414855.xml · nonDerivative · entry 2

Miller Melissa F. (Missy) · CIK 0001998251 · Chief Marketing Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 201,956

F1 · kind: This Form 4/A is being filed to correct the original Form 4 filed on May 15, 2025 ("Original Form 4"). The Original Form 4 inadvertently omitted the reporting of an option exercise that occurred on May 15, 2025, immediately prior to the sale of shares reported in that filing. The number of shares sold as reported in the Original Form 4 was correct; however, the ending total was incorrect due to the omission of the option exercise. This amendment adds the previously unreported option exercise transaction and restates the sell of shares reported in the Original Form 4 in a single combined row, consistent with other filings for the Reporting Owner. No other changes have been made to the Original Form 4.

F4 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $38.89 to $40.06, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F2 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 20, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

F3 · balance_after: Includes unvested RSUs.

SEC source: 0001998251-25-000004 · wk-form4a_1756414855.xml · nonDerivative · entry 1

Miller Melissa F. (Missy) · CIK 0001998251 · Chief Marketing Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 205,356

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: This Form 4/A is being filed to correct the original Form 4 filed on May 15, 2025 ("Original Form 4"). The Original Form 4 inadvertently omitted the reporting of an option exercise that occurred on May 15, 2025, immediately prior to the sale of shares reported in that filing. The number of shares sold as reported in the Original Form 4 was correct; however, the ending total was incorrect due to the omission of the option exercise. This amendment adds the previously unreported option exercise transaction and restates the sell of shares reported in the Original Form 4 in a single combined row, consistent with other filings for the Reporting Owner. No other changes have been made to the Original Form 4.

F2 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 20, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

F3 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-048683 · tm2515110-1_4seq1.xml · derivative · entry 4

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 1,672,881

Underlying: Common Stock · 46,667 shares

Expires 2027-11-01

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-048683 · tm2515110-1_4seq1.xml · nonDerivative · entry 3

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 764,131

F3 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of Issuer were sold in multiple transactions ranging from $39.41 to $39.68, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-048683 · tm2515110-1_4seq1.xml · nonDerivative · entry 2

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 766,835

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $38.41 to $39.40, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-048683 · tm2515110-1_4seq1.xml · nonDerivative · entry 1

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 810,798

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-047354 · tm2514848-1_4seq1.xml · derivative · entry 3

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 129,355

Underlying: Common Stock · 8,623 shares

Expires 2027-11-01

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-047354 · tm2514848-1_4seq1.xml · nonDerivative · entry 2

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 438,044

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $39.97 to $40.58, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-047354 · tm2514848-1_4seq1.xml · nonDerivative · entry 1

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 446,667

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-047057 · tm2514762-1_4seq1.xml · nonDerivative · entry 1

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 764,131

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-034705 · tm2512190-2_4seq1.xml · derivative · entry 4

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 137,978

Underlying: Common Stock · 8,623 shares

Expires 2027-11-01

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034705 · tm2512190-2_4seq1.xml · nonDerivative · entry 3

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 438,044

F3 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were sold in multiple transactions ranging from $36.63 to $37.05, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034705 · tm2512190-2_4seq1.xml · nonDerivative · entry 2

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 440,557

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $35.63 to $36.62, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034705 · tm2512190-2_4seq1.xml · nonDerivative · entry 1

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 446,667

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034704 · tm2512190-1_4seq1.xml · derivative · entry 4

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 2,469,548

Underlying: Common Stock · 46,667 shares

Expires 2027-11-01

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034704 · tm2512190-1_4seq1.xml · nonDerivative · entry 3

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 500,000

F3 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of Issuer were sold in multiple transactions ranging from $36.47 to $37.18, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034704 · tm2512190-1_4seq1.xml · nonDerivative · entry 2

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 520,121

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $35.47 to $36.46, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-034704 · tm2512190-1_4seq1.xml · nonDerivative · entry 1

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 546,667

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-031490 · tm2511308-3_4seq1.xml · nonDerivative · entry 1

Wittman Kimberly S. · CIK 0002020858 · Chief People Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 201,956

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-031494 · tm2511308-6_4seq1.xml · nonDerivative · entry 1

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 438,044

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-031493 · tm2511308-5_4seq1.xml · nonDerivative · entry 1

Bridge T. Craig · CIK 0001998332 · Chief Transformation Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 783,789

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-031496 · tm2511308-7_4seq1.xml · derivative · entry 2

PACKER GREGORY R · CIK 0001735839 · Chief Legal Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 132,065

Underlying: Common Stock · 132,065 shares

Expires 2035-04-01

F3 · kind: On April 1, 2025 reporting person was granted options to purchase shares of Common Stock which vest in four substantially equal annual installments commencing on April 1, 2026.

F3 · derivative.exercise_date: On April 1, 2025 reporting person was granted options to purchase shares of Common Stock which vest in four substantially equal annual installments commencing on April 1, 2026.

SEC source: 0001104659-25-031496 · tm2511308-7_4seq1.xml · nonDerivative · entry 1

PACKER GREGORY R · CIK 0001735839 · Chief Legal Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 52,826

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest in four substantially equal annual installments commencing on April 1, 2026. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-031491 · tm2511308d4_4seq1.xml · nonDerivative · entry 1

Miller Melissa F. (Missy) · CIK 0001998251 · Chief Marketing Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 201,956

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-031488 · tm2511308-1_4seq1.xml · nonDerivative · entry 1

Oreskovich Steven M · CIK 0001368470 · Chief Financial Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 384,946

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-031489 · tm2511308-2_4seq1.xml · nonDerivative · entry 1

Sinclair III Eric L. (Ric) · CIK 0001998250 · Chief Business Officer

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 490,870

F1 · kind: Reflects a grant of restricted stock units ("RSUs") which vest over 4 years, with 40% vesting in year 3 and 60% vesting in year 4. Each RSU represents a contingent right to receive one share of common stock, $0.01 par value per share (the "Common Stock") upon settlement.

F2 · balance_after: Includes unvested RSUs.

SEC source: 0001104659-25-023981 · tm259049-2_4seq1.xml · derivative · entry 4

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 2,516,215

Underlying: Common Stock · 46,665 shares

Expires 2027-11-01

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023981 · tm259049-2_4seq1.xml · nonDerivative · entry 3

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 500,000

F3 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of Issuer were sold in multiple transactions ranging from $36.19 to $36.80, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023981 · tm259049-2_4seq1.xml · nonDerivative · entry 2

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 500,500

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $35.17 to $36.03, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023981 · tm259049-2_4seq1.xml · nonDerivative · entry 1

Hawkins Matthew J. · CIK 0001998256 · Director · Chief Executive Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 546,665

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 22, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023980 · tm259049-1_4seq1.xml · derivative · entry 4

Oreskovich Steven M · CIK 0001368470 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 117,871

Underlying: Common Stock · 16,666 shares

Expires 2028-09-17

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on September 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023980 · tm259049-1_4seq1.xml · nonDerivative · entry 3

Oreskovich Steven M · CIK 0001368470 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 173,642

F3 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of Issuer were sold in multiple transactions ranging from $37.74 to $38.37, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on September 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023980 · tm259049-1_4seq1.xml · nonDerivative · entry 2

Oreskovich Steven M · CIK 0001368470 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 174,342

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $36.70 to $37.66, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on September 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-023980 · tm259049-1_4seq1.xml · nonDerivative · entry 1

Oreskovich Steven M · CIK 0001368470 · Chief Financial Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 190,308

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on September 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · derivative · entry 8

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 146,601

Underlying: Common Stock · 8,623 shares

Expires 2027-11-01

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F7 · derivative.exercise_date: These options are currently vested.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 7

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 173,913

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 6

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 174,013

F6 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were sold in multiple transactions ranging from $39.54 to $40.49, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 5

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 174,913

F5 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were sold in multiple transactions ranging from $38.54 to $39.00, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 4

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 175,213

F4 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were sold in multiple transactions ranging from $37.27 to $37.69, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 3

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 178,785

F3 · price: The price reported in Column 4 is a weighted average price. These shares of Common Stock of the Issuer were sold in multiple transactions ranging from $36.25 to $37.24, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 2

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 180,972

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $35.23 to $36.15, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-022577 · tm258784-1_4seq1.xml · nonDerivative · entry 1

Schremser Christopher L. · CIK 0001998333 · Chief Technology Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 182,536

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on December 6, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-019346 · tm257974-1_4seq1.xml · derivative · entry 3

Bridge T. Craig · CIK 0001998332 · Chief Transformation Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 262,167

Underlying: Common Stock · 131,083 shares

Expires 2029-10-23

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · derivative.exercise_date: These options were vested at the time of the Issuer's initial public offering.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 27, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-019346 · tm257974-1_4seq1.xml · nonDerivative · entry 2

Bridge T. Craig · CIK 0001998332 · Chief Transformation Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 519,658

F2 · price: The price reported in Column 4 is a weighted average price. These shares of common stock, par value $0.01 per share ("Common Stock") of Waystar Holding Corp. (the "Issuer") were sold in multiple transactions ranging from $41.66 to $42.44, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price in the range set forth in this footnote.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 27, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0001104659-25-019346 · tm257974-1_4seq1.xml · nonDerivative · entry 1

Bridge T. Craig · CIK 0001998332 · Chief Transformation Officer

10b5-1 filing: Plan reported

Ownership: Direct

Disclosed balance after: 702,572

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · balance_after: These transactions occurred automatically pursuant to a plan adopted by the Reporting Person on November 27, 2024 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

SEC source: 0000950170-25-028174 · ownership.xml · nonDerivative · entry 2

BAIN CAPITAL INVESTORS LLC · CIK 0001040508 · 10% owner

BCPE Derby Investor, LP · CIK 0002025342 · 10% owner

BCPE Derby GP, LLC · CIK 0002025234 · 10% owner

Bain Capital Fund XI, L.P. · CIK 0001568889 · 10% owner

Bain Capital Partners XI, L.P. · CIK 0001851748 · 10% owner

BCPE Derby (DE) SPV, LP · CIK 0002048434 · 10% owner

BCPE Derby (DE) SPV (GP), LLC · CIK 0002048242 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 21,754,536

F4 · kind: 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.

F4 · price: 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.

F1 · ownership.nature: 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 BCPE Derby Investor, LP ("Derby Investor") and (ii) sole member of BCPE Derby (DE) SPV, LLC ("Derby SPV GP"), which is the general partner of BCPE Derby (DE) SPV, LP ("Derby SPV Investor" and, together with BCI, Partners XI, Fund XI, Derby GP, Derby Investor and Derby SPV GP, the "Bain Capital Entities").

F2 · ownership.nature: (Continued from footnote 1) As a result, the Bain Capital Entities 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 Derby Investor and Derby SPV Investor. The Bain Capital Entities disclaims beneficial ownership of such securities, except to the extent of their pecuniary interest therein.

SEC source: 0000950170-25-028174 · ownership.xml · nonDerivative · entry 1

BAIN CAPITAL INVESTORS LLC · CIK 0001040508 · 10% owner

BCPE Derby Investor, LP · CIK 0002025342 · 10% owner

BCPE Derby GP, LLC · CIK 0002025234 · 10% owner

Bain Capital Fund XI, L.P. · CIK 0001568889 · 10% owner

Bain Capital Partners XI, L.P. · CIK 0001851748 · 10% owner

BCPE Derby (DE) SPV, LP · CIK 0002048434 · 10% owner

BCPE Derby (DE) SPV (GP), LLC · CIK 0002048242 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 22,327,728

F3 · kind: 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).

F3 · price: 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).

F1 · ownership.nature: 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 BCPE Derby Investor, LP ("Derby Investor") and (ii) sole member of BCPE Derby (DE) SPV, LLC ("Derby SPV GP"), which is the general partner of BCPE Derby (DE) SPV, LP ("Derby SPV Investor" and, together with BCI, Partners XI, Fund XI, Derby GP, Derby Investor and Derby SPV GP, the "Bain Capital Entities").

F2 · ownership.nature: (Continued from footnote 1) As a result, the Bain Capital Entities 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 Derby Investor and Derby SPV Investor. The Bain Capital Entities disclaims beneficial ownership of such securities, except to the extent of their pecuniary interest therein.

SEC source: 0000950170-25-028175 · ownership.xml · nonDerivative · entry 2

Moskowitz Paul G · CIK 0001997404 · Director · 10% owner

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 21,754,536

F4 · kind: 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.

F4 · price: 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.

F1 · ownership.nature: 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").

F2 · ownership.nature: (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.

SEC source: 0000950170-25-028175 · ownership.xml · nonDerivative · entry 1

Moskowitz Paul G · CIK 0001997404 · Director · 10% owner

10b5-1 filing: No plan indicated

Ownership: Indirect · See Footnote

Disclosed balance after: 22,327,728

F3 · kind: 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).

F3 · price: 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).

F1 · ownership.nature: 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").

F2 · ownership.nature: (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.

SEC source: 0000950170-25-027810 · ownership.xml · nonDerivative · entry 1

Derby LuxCo S.a r.l. · CIK 0001998443 · 10% owner

EQT Fund Management S.a r.l. · CIK 0001834239 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · Held directly by Derby LuxCo

Disclosed balance after: 38,828,374

F1 · ownership.nature: 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.