To file B&O tax in Washington State, log into the Department of Revenue’s MyDOR portal with your Unified Business Identifier, sort your gross income into the correct tax classifications, enter deductions and credits, then submit the return and pay by your assigned due date. The tax runs on gross receipts, so there’s no subtracting cost of goods, payroll, or overhead before you calculate what you owe. Everything below walks through the numbers you’ll plug in, the deadlines the Department assigns, and the sequence inside MyDOR.
What You Need Before You Open the Return
Three things sit in front of every clean filing.
Your Unified Business Identifier (UBI) is the nine-digit number issued when you registered your business in Washington, and it’s your account key for everything on MyDOR.1Washington Department of Revenue. Business Licensing and Renewals FAQs
Your gross income totals need to be broken out by tax classification, not lumped together. A store that also does repair work has retailing income on one line and service income on another. A manufacturer that sells its own product in-state reports under two classifications and then uses a credit to avoid paying twice on the same dollars. Sorting this before you start is what keeps you from filing an amended return later.
Your filing frequency has already been assigned by the Department based on your expected annual tax. You’ll see it inside your MyDOR account. If your revenue has shifted significantly, the Department can move you between schedules.
One threshold question for out-of-state sellers: you owe Washington B&O tax if your combined gross receipts sourced to Washington exceed $100,000 in the current or prior calendar year, even without a physical presence here.2Washington Department of Revenue. Out of State Businesses Reporting Thresholds and Nexus
2026 Classifications and Rates
The Department taxes different activities at different rates, and every line on the return has its own. Putting revenue on the wrong line is one of the fastest ways to trigger an assessment.3Washington Department of Revenue. Business and Occupation (B&O) Tax
- Retailing: 0.471 percent. Sales of goods and certain services to end consumers.
- Wholesaling: 0.484 percent. Sales to other businesses for resale.
- Manufacturing: 0.484 percent, applied to the value of products manufactured in Washington.
Service and Other Activities changed on January 1, 2026 and now runs on three tiers based on your prior calendar year’s taxable service income:4Washington Department of Revenue. Service and Other Activities Rate Changes
- Under $1 million: 1.5 percent
- $1 million to $4,999,999: 1.75 percent
- $5 million or more: 2.1 percent
If your business is part of an affiliated group, the tier is set by the group’s combined service income in the prior year, not just yours. A member entity below $1 million can still report at the higher rate because of the group’s total. Hospitals pay 1.5 percent regardless of revenue.5Washington State Legislature. Washington Code 82.04.290 – Tax on Service and Other Activities
Deductions and Credits to Apply on the Return
Because the tax hits gross receipts, the deductions and credits are where your bill actually shrinks. Enter the full gross amount on the classification line first, then take the deduction or credit on its own line.
Small Business Credit
MyDOR calculates this credit automatically from the figures you enter. The maximum is $160 per reporting month if at least half your taxable amount comes from service activities, royalties, or similar classifications; it’s $55 per month for everyone else. For annual filers that works out to $1,920 or $660. Below the maximum, the credit erases your tax entirely; above it, the credit phases out on a sliding scale until it hits zero.6Washington State Legislature. Washington Code RCW 82.04.4451 – Credit Against Tax Due, Maximum Credit, Table
Interstate and Out-of-State Sales
Revenue from goods delivered to buyers outside Washington is generally not taxable. Enter the full gross amount under the appropriate classification, then claim the interstate deduction on its own line under RCW 82.04.4286.7Washington State Legislature. Washington Code RCW 82.04.4286 – Deductions, Nontaxable Business
Apportionment for Multi-State Service Income
Service income taxable in Washington and another state gets apportioned, not deducted transaction by transaction. You report your total apportionable income, then take an apportionment deduction sized by the percentage of receipts attributed to Washington under the state’s single-factor receipts formula.8Washington Department of Revenue. Apportionment – The Basics
Multiple Activities Tax Credit
If you manufacture in Washington and also sell that product here, you’ll show income on both the Manufacturing line and the Retailing or Wholesaling line. The Multiple Activities Tax Credit (MATC) prevents the double hit on the overlapping dollars. Both the manufacturing tax and the selling tax must actually be paid before you claim it.9Washington Department of Revenue. Multiple Activities Tax Credit (MATC)
Filing Frequency and Due Dates
The Department slots you into one of three schedules based on your annual tax liability:10Cornell Law Institute. Washington Administrative Code 458-20-22801 – Tax Reporting Frequency
- Monthly: annual tax liability over $4,800
- Quarterly: between $1,050 and $4,800
- Annual: under $1,050
Due dates by schedule:11Washington Department of Revenue. Filing Frequencies and Due Dates
- Monthly: the 25th of the following month. June activity is due July 25.
- Quarterly: the last day of the month after the quarter closes. Q1 April 30, Q2 July 31, Q3 October 31, Q4 January 31.
- Annual: April 15 of the following year.
Zero-revenue periods still require a return. Skipping a filing because you owe nothing triggers the same late-filing penalty as skipping one with a balance.12Washington Department of Revenue. Instructions for Completing the Combined Excise Tax Return
Filing the Return in MyDOR
Log into MyDOR and open the electronic return for your assigned period.
Enter gross receipts on each applicable classification line: Retailing, Wholesaling, Manufacturing, Service and Other Activities, and any others that apply to your activity. Enter deductions (interstate sales, apportionment, other statutory deductions) on the corresponding deduction lines beneath each classification.
The system calculates the tax, applies the small business credit if you qualify, and generates a summary showing what’s owed under each classification. Check the summary against your own books. A misclassified revenue line caught here is a two-minute fix; caught later it’s an amended return.
Once the summary is right, click through to the submission screen and hit Submit. MyDOR then prompts you to pay.
Paying and Saving Proof
ACH Debit pulls funds from your bank account at no additional charge. Credit card payments (Visa, Mastercard, American Express, Discover) go through a third-party processor that charges a convenience fee.13Washington Department of Revenue. Payment Methods
After the payment processes, MyDOR issues a confirmation number. That number is your proof of timely filing, and the filing isn’t complete until you have it. Save or print both the confirmation and the PDF copy of the return. Keep them with your records for at least five years, the Department’s minimum retention period for business tax documentation.14Washington Department of Revenue. Record Keeping Requirements
If You’re Late or Need More Time
Late-payment penalties climb quickly. Miss the due date and you owe 9 percent of the tax due immediately. If payment still hasn’t arrived by the last day of the following month, it jumps to 19 percent. Two months late brings it to 29 percent. The minimum penalty is $5.15Washington State Legislature. Washington Code 82.32.090 – Late Payment, Penalties Interest runs on top of that: 6 percent annual interest on unpaid tax for calendar year 2026.16Washington Department of Revenue. Interest Rate Tables
You can request a penalty waiver in writing within 30 days of receiving the penalty notice, but only when the late filing was caused by circumstances genuinely beyond your control: a fire that destroyed records, serious illness affecting you or your accountant, a system failure that blocked electronic filing. Financial hardship, misunderstanding the law, and employee mistakes generally don’t qualify.17Cornell Law Institute. Washington Administrative Code 458-20-228 – Returns, Payments, Penalties, Extensions, Interest, Stays of Collection
There’s also a clean-record waiver. If you’ve filed and paid on time for the 24 months before the delinquent period, you can request a one-time waiver of the late-payment penalty. Businesses operating under 24 months qualify if they have no prior delinquencies.17Cornell Law Institute. Washington Administrative Code 458-20-228 – Returns, Payments, Penalties, Extensions, Interest, Stays of Collection
If you know in advance you’ll be late, request an extension before the original due date through MyDOR, by calling 360-705-6705, or by secure email. The Department grants extensions for computer failures, lost or destroyed records, medical emergencies, and natural disasters. Cash flow problems and slow business don’t qualify. Once the due date passes without an extension on file, your only remaining option is to file late and request a waiver.18Washington Department of Revenue. Excise Tax Return Extensions
Amending a Return
Errors caught after submission get fixed through an amended return in MyDOR. An amended return showing an overpayment doubles as a refund application, but you have to specifically identify what caused the overpayment. The refund deadline is four years before the beginning of the calendar year in which you file the amended return, and it’s a hard cutoff.19Cornell Law Institute. Washington Administrative Code 458-20-229 – Refunds
City B&O Taxes Are a Separate Filing
Filing your state return does not cover local B&O tax. Dozens of Washington cities impose their own B&O taxes with separate rates, thresholds, and filing systems, and city thresholds are often much lower than the state’s $100,000. Seattle, Bellevue, Tacoma, Everett, Kent, Renton, and many others run local B&O taxes; Vancouver’s took effect January 1, 2026.
A group of cities uses the FileLocal portal, which lets you file local returns and apply for business licenses in one place. Participants include Seattle, Bellevue, Tacoma, Everett, Kent, Auburn, Des Moines, Lake Forest Park, Renton, and Shoreline.20FileLocal. FileLocal – Frequently Asked Questions Cities outside FileLocal require you to file directly with their finance departments. Check each city where you conduct business.