The Washington Department of Revenue (DOR) released an Interim Guidance Statement (IGS) on Advertising Services implementing Engrossed Substitute Senate Bill (ESSB) 5814 ahead of the October 1, 2025, effective date. In previous posts, we addressed the passage of ESSB 5814 and the sourcing rules. The Advertising Services IGS is part of a broader rollout of interim guidance DOR is publishing before the effective date.