DOR: Contractors pay sales tax on clean-up activities
The State Department of Revenue reminds contractors that sales taxes must be paid on janitorial services that are construction clean-up or preparation for turning a new building over to the owner. The DOR prepared this webpage describing when a retail sales tax is applicable for interior cleaning services.
Plus the specific law that references this is WAC 458-20-172. It states that “Persons engaged in performing contracts for the… cleaning… of existing buildings or structures must collect the retail sales tax upon the full contract price when the work is performed for consumers.”