Washington sales tax is filed online in My DOR, the Department of Revenue's secure portal, on the Combined Excise Tax Return. Monthly returns are due the 25th of the following month, quarterly returns are due the end of the month after the quarter, and annual returns are due April 15. The Department requires all businesses to file and pay electronically.
This guide covers who files and how often, how to file in My DOR, how to report no activity, how to amend a return, how to pay, and what late filing costs.
This article is educational information, not tax advice. Filing rules, thresholds, and penalties can change, so confirm current requirements with the Washington Department of Revenue before you file.
Washington sales tax filing at a glance
- Who administers it: Washington Department of Revenue.
- Online portal: My DOR, at secure.dor.wa.gov.
- Return: Combined Excise Tax Return, which reports Business and Occupation (B&O) tax, state and local sales and use tax, and other taxes together.
- Filing frequency: Monthly, quarterly, or annual, assigned by the Department.
- Due dates: Monthly on the 25th, quarterly at the end of the month after the quarter, annual on April 15. A due date on a weekend or legal holiday moves to the next business day.
- Zero returns: Required. File through My DOR, Express File with no login, or by phone.
- Payment: EFT debit, EFT credit, e-check, or card. Paper check and cash only with a waiver.
- Economic nexus: More than $100,000 in combined gross receipts sourced or attributed to Washington.
Who has to file, and how often
Every business registered with the Department of Revenue files a Combined Excise Tax Return for each assigned period. That includes remote sellers. The Department says a remote seller must register if it has more than $100,000 in combined gross receipts sourced or attributed to Washington in the current or prior year, or if it is organized or commercially domiciled in Washington. Exempt sales count toward the threshold. Our Washington sales tax guide covers registration and nexus in more detail. Selling software? Our post on Washington SaaS sales tax explains how it is treated there.
The Department assigns your frequency, based on your estimated income and annual tax liability, and sends it in a welcome letter after you register. By annual tax liability:
| Frequency | Annual tax liability | Due date |
|---|---|---|
| Annual | $1,050 or less | April 15 |
| Quarterly | $1,051 to $4,800 | End of the month following the quarter |
| Monthly | $4,801 or more | The 25th of the following month |
To request a change in frequency, call the Department at 360-705-6705.
Before you start: get into My DOR
You need to be registered with the Department of Revenue before you can file; our sales tax permit overview explains the process. You sign in to My DOR with Secure Access Washington (SAW) credentials. Before filing, gather your records for the period: gross receipts by activity, retail sales by delivery location, and any deductions or credits you claim. For wholesale sales, see our Washington resale certificate guide for what to collect from buyers.
Step-by-step: filing a Washington return in My DOR
- Log in to My DOR and open the Excise Tax Return panel.
- Select File Return and choose the reporting period.
- Report B&O tax. Section I of the Combined Excise Tax Return covers Business and Occupation tax by classification.
- Report retail sales tax by location. Retailers report state and local sales tax by location and tax rate code. Washington sales tax is destination-based, so the rate depends on where the customer receives the item.
- Add other taxes and credits. The return also has sections for lodging and other taxes and for credits.
- Review and submit. Sign and submit electronically, then pay.
Filing in Washington plus other states? Kintsugi files and remits for you, from $75 per filing, with free monitoring. Book a demo or start free.
Local and destination-based rate pitfalls
Washington returns are built around location codes, so a wrong address means a wrong rate. The Department offers a tax rate lookup tool that returns the correct rate and location code for an address, a batch service for spreadsheets of addresses, and a downloadable rate database updated quarterly. Look up each delivery address rather than reusing one rate for every sale. Our Washington sales tax calculator shows current rates by location.
Due dates and the weekend rule
For 2026, the Department publishes these dates (you can also see them on our Washington sales tax due dates page):
| Period | Due date |
|---|---|
| Monthly, January through November | The 25th of the following month (January is due 02/25/26) |
| Monthly, December | 01/25/27 |
| Quarter 1 | 04/30/26 |
| Quarter 2 | 07/31/26 |
| Quarter 3 | 10/31/26 |
| Quarter 4 | 01/31/27 |
| Annual (2026 return) | 04/15/27 |
If a due date falls on a weekend or legal holiday, it is extended to the next business day.
Filing a zero return
You must file even if you had no business activity. The Department offers three ways:
- Express File: Report online with no login required.
- My DOR: In the Excise Tax Return panel, click File Return, then select Report No Business.
- Phone: Call 360-705-6705 and follow the prompts. You need your 9-digit Account ID. You do not need to mail a paper return.
Amending a return
To correct a filed return, use the Amend my return section in My DOR. The Department says you may go back four years, plus the current year.
Payment methods
- EFT debit: You authorize the Department to withdraw funds from your bank account. No cost.
- EFT credit: You tell your bank to send funds to the state. Your bank may charge a fee.
- E-check: Free, but you enter bank account details for each payment.
- Credit or debit card: American Express, Discover, MasterCard, and Visa, with a convenience fee.
- Check or cash: Only if you received a waiver from the mandatory e-file and e-pay requirement.
Penalties and interest for late payment
The Department must assess a 9% penalty if the tax due on a return is not paid by the due date. Penalties then rise to 19% after the last day of the month following the due date, and to 29% after the last day of the second month following the due date. The minimum late-payment penalty is $5. Interest rates for delinquent accounts are published in the Department's interest rate tables and change annually.
The Department can waive late penalties in certain circumstances, and you can request a waiver if you have a qualifying situation. Requests for an extension must be made before the due date.
Common mistakes to avoid
- Skipping zero returns. Every assigned period needs a return, even with no activity.
- Using one rate for every sale. Sourcing is by destination, so look up each address.
- Missing the quarterly or annual date. Quarterly returns are not due on the 25th; they are due at the end of the month after the quarter.
- Waiting for a paper form. Paper filing requires a waiver.
- Counting only taxable sales toward nexus. Exempt sales count toward the $100,000 threshold.
More state filing guides
Filing in more than one state? These step-by-step guides cover the portals, due dates, and penalties in other states. See them all in our state-by-state guide to filing sales tax online.
- How to file California sales tax online
- How to file Illinois sales tax online
- How to file Georgia sales tax online
Let Kintsugi file for you
If you sell in Washington and other states, Kintsugi's sales tax filing software prepares and files returns on each state's assigned schedule and remits payment. Monitoring across every US state is free, so you know when you cross a threshold. Filing starts at $75 per filing, with no per-state subscription. See pricing, start free, or book a demo.
Frequently asked questions
Can I file Washington sales tax online for free?
Yes. Filing in My DOR has no fee. The Department charges a convenience fee only for card payments.
What form do I use to file Washington sales tax?
The Combined Excise Tax Return, filed electronically in My DOR. It reports B&O tax and sales and use tax together.
When is Washington sales tax due?
Monthly returns are due the 25th of the following month. Quarterly returns are due the end of the month after the quarter, and annual returns are due April 15.
Do I have to file if I had no sales?
Yes. Use Express File, My DOR, or phone at 360-705-6705 to report no business activity.
What is the economic nexus threshold in Washington?
More than $100,000 in combined gross receipts sourced or attributed to Washington, in the current or prior year.
What if I miss the deadline?
File and pay as soon as possible. A 9% penalty applies to unpaid tax after the due date, rising to 19% and 29% in later months, and you can ask for a penalty waiver.
Sources
Checked September 29, 2026.
- Washington Department of Revenue, File & pay taxes
- Washington Department of Revenue, Filing frequencies and due dates
- Washington Department of Revenue, 2026 excise tax return due dates
- Washington Department of Revenue, Instructions for completing the Combined Excise Tax Return
- Washington Department of Revenue, Payment methods
- Washington Department of Revenue, Report no business activity
- Washington Department of Revenue, Late filing and Penalty waivers
- Washington Department of Revenue, Remote sellers
- Washington Department of Revenue, Tax rate lookup tool
