Washington State became the nineteenth full member on the Streamlined Sales Tax (“SST”)Governing Board, effective July 1, 2008. Previously, an associate member state, Washington amended its sales tax laws in 2007 and 2008 to conform to the SST Agreement. The effective date, July 1, 2008, is the date its conformity provisions, including destination-based sales tax collection took effect. All sellers registered under the SST Agreement now must collect tax on sales in Washington. (Streamlined Sales Tax Governing Board, Inc.)