Tax Included in Retail Sale Price

Effective July 21, 2008 sales tax must be listed separately on all retail taxable sales invoices. Sales tax can no longer be included in the retail sale price. If not stated separately the retailer is liable for remitting applicable sales taxes on the total amount of the invoice.
References
RCW 82.08.050 - Buyer to pay, seller to collect tax -- Statement of tax -- Exception -- Penalties -- Contingent expiration of subsection.
WAC 458-20-107 - Requirement to separately state sales tax -- Advertised prices including sales tax.