Washington B&O guide
How to file the Washington Business & Occupation Tax
A practical walk-through of filing the Washington B&O — what to gather, where to file, the deadlines, and the mistakes that trip people up.
Last reviewed June 2026 against Washington State Department of Revenue guidance.
What you'll need
- Gross receipts for each business activity (no cost deductions)
- A MyDOR (SecureAccess Washington) account
Step by step
- 1Register with the Department of Revenue if your Washington receipts exceed $100,000.
- 2Classify each activity (Retailing, Wholesaling, Manufacturing, Service & Other Activities, etc.).
- 3Report gross receipts for each classification on the Combined Excise Tax Return.
- 4Apply the Small Business B&O Tax Credit if you qualify, then file via MyDOR on your assigned monthly, quarterly, or annual schedule.
Where to file
Combined Excise Tax Return (B&O reported within it)
Filed via MyDOR
Official form / filing portalDeadlines
Monthly, quarterly, or annual (by tax liability).
- Monthly filers25th of next month
- Quarterly filersEnd of next month
- Annual filersApril 15
Common mistakes to avoid
- There is no deduction for costs — B&O is on gross receipts.
- A single business can owe under several classifications at once.
- Don't overlook the Small Business B&O Tax Credit, which can reduce or eliminate the tax for small filers.
Estimate your Washington B&O and get a pre-filled worksheet first.
Open calculatorGeneral information, not tax advice — confirm the current procedure with the Washington State Department of Revenue or a qualified CPA before filing.