from the Department of Revenue…
The B&O tax is a gross receipts tax. It is measured on the value of products, gross proceeds of sale, or gross income of the business.
Washington, unlike many other states, does not have an income tax. Washington’s B&O tax is calculated on GROSS income from activities. This means there are no deductions from the B&O tax for labor, materials, taxes, or other costs of doing business.
The Business and Occupation (B&O) tax is a gross receipts tax levied on a business for the privilege of doing business in Washington. Almost all businesses located or doing business in the state of Washington are subject to the state B&O tax. It is an out-of-pocket cost for engaging in business activities.
The classification and rate of the B&O tax are based on the type of business activity conducted in this state. A business may perform more than one type of activity. Businesses performing multiple activities may be subject to tax under one or more B&O tax classifications.