There is no personal income tax in Washington State. What is the average Washington sales tax rate? 8.78%. The state has a 6.5% tax, but the average local tax is The 1889 state constitution recognized that to be effective, uniformity must apply to both assessments and tax rates. major tax that supported most state and local government 30 May 2019 The B&O tax rate varies depending on the classification of a taxpayer's instead of substantially expanding its presence in Washington state.