Clearwater Paper Corp

Rule 10b5-1 Trading Arrangements

During the quarter ended September 30, 2025, the following officer (as defined in Rule 16a-1(f) of the Exchange Act)adopted a Rule 10b5-1 trading arrangement, as defined in Item 408 of Regulation S-K, for the sale of our common stock. Shares in the 10b5-1 trading arrangement that are subject to restricted stock units (“RSUs”) and stock options may only be traded following satisfaction of applicable vesting requirements. In addition, because of pricing (such as future share price targets) and timing conditions in the 10b5-1 trading arrangement, it is not yet determinable how many shares actually will be sold under the plan prior to its expiration date.

On August 29, 2025, Steve Bowden, our Senior Vice President, Operations, entered into a Rule 10b5-1 trading arrangement that provides for the sale of up to 8,889 shares of our common stock. This trading arrangement is scheduled to expire on December 31, 2025.

This Rule 10b5-1 trading arrangement was entered into in writing during an open trading window, includes the mandatory cooling-off period and good-faith certification required by Rule 10b5-1(c)(1), and is intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Exchange Act and our policies regarding transactions in our securities.

During the quarter ended September 30, 2025, none of our other officers or directors adopted orterminated a Rule 10b5-1 arrangement or non-Rule 10b5-1 trading arrangement, as each is defined in Item 408(a) of Regulation S-K.