Material Event (Form 8-K)

On September 10, 2025, Waystar Holding Corp. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") by and among the Company, the selling stockholders named in Schedule 2 thereto (the "Selling Stockholders") and J.P. Morgan Securities LLC, relating to an underwritten offering of 18,000,000 shares (the "Shares") of the Company's common stock, par value $0.01 per share, pursuant to the Company's Registration Statement on Form S-3 (File No. 333-288662), filed on July 14, 2025. The Company did not sell any Shares in the offering. The offering is expected to close on September 12, 2025, subject to customary closing conditions. The Company will not receive any proceeds from the offering.

The description of the Underwriting Agreement is qualified in its entirety by the terms of such agreement, which is incorporated herein by reference and attached to this report as Exhibit 1.1.