Bain Capital Entities' Share Transactions in Waystar Holding Corp.

On September 12, 2025, Bain Capital Entities, including BCPE Derby Investor, LP and BCPE Derby (DE) SPV, LP, sold a total of 4,295,139 shares of Waystar Holding Corp.'s common stock at a price of $39.21 per share. Additionally, 516,371 shares were distributed to members or partners in connection with charitable gifts, subject to lock-up agreements restricting sale until November 11, 2025. The Bain Capital Entities disclaim beneficial ownership of these shares except to the extent of their pecuniary interest. The transactions were reported in a Form 4 filing.