RCW 40.07.070

A state agency may not accept advertising for placement in a state publication unless the advertiser: (1) Has obtained a certificate of registration from the department of revenue under chapter 82.32 RCW; and (2) if the advertiser is not otherwise obligated to collect and remit Washington retail sales tax or use tax, the advertiser either (a) agrees to voluntarily collect and remit the Washington use tax upon all sales to Washington consumers, or (b) agrees to provide to the department of revenue, no less frequently than quarterly, a listing of the names and addresses of Washington customers to whom sales were made. This section does not apply to advertising that does not offer items for sale or to advertising that does not solicit orders for sales.