Washington Business Tax Deadlines (2026)
Next: April 25 — WA B&O Tax and Sales Tax monthly return due
Next Deadline: April 25 — WA B&O Tax and Sales Tax monthly return due
Federal Tax Deadlines (2026)
| Form | Who Files | Due Date | Extension Deadline |
|---|---|---|---|
| Form 1040 (Schedule C) | Sole proprietors | April 15 | October 15 |
| Form 1065 | Partnerships, Multi-member LLCs | March 15 | September 15 |
| Form 1120-S | S-Corporations | March 15 | September 15 |
| Form 1120 | C-Corporations | April 15 | October 15 |
| Form 990 | Nonprofits | May 15 | November 15 |
| Estimated Taxes (Q1-Q4) | All | Apr 15, Jun 15, Sep 15, Jan 15 2027 | — |
Washington State Tax Deadlines (2026)
| Tax Type | Who Files | Due Date | Extension Deadline |
|---|---|---|---|
| Individual Income Tax | None — Washington has no personal income tax | N/A | N/A |
| Corporate Income Tax | None — Washington has no corporate income tax | N/A | N/A |
| Capital Gains Tax | Individuals with capital gains over $270,000 | April 15 | October 15 |
| Business & Occupation (B&O) Tax | All businesses with WA activity | Monthly (25th), quarterly, or annual | — |
| Sales & Use Tax | Businesses with taxable sales | Monthly (25th), quarterly, or annual | — |
| Payroll — Employer Withholding | None — no state income tax to withhold | N/A | N/A |
| Payroll — Unemployment Insurance | Employers | Quarterly (last day of month following quarter) | — |
| Payroll — Paid Family & Medical Leave | Employers | Quarterly (last day of month following quarter) | — |
| Annual Report | Corporations and LLCs | Anniversary of formation month | — |
Quarterly Estimated Tax Deadlines in Washington
Washington has no personal income tax (the state's capital gains tax is an excise tax on capital gains over $270,000, not a traditional income tax). There are no state estimated income tax payments.
B&O Tax and Sales Tax follow their own schedules based on filing frequency:
| Filing Frequency | Due Dates |
|---|---|
| Monthly | 25th of the following month |
| Quarterly | Apr 25, Jul 25, Oct 25, Jan 25 2027 |
| Annual | January 31, 2027 (for tax year 2026) |
Your filing frequency is assigned by the Department of Revenue based on your estimated tax liability.
Washington-Specific Tax Requirements
Washington is one of nine states with no personal income tax. The state constitution has historically been interpreted to prohibit a graduated income tax. In 2021, Washington enacted a 7% Capital Gains Tax on gains over $250,000 (threshold adjusted to approximately $270,000 for 2026) from the sale of long-term capital assets. The state supreme court upheld this as an "excise tax." Real estate, retirement accounts, and certain small business sales are exempt.
Washington's primary business tax is the Business & Occupation (B&O) Tax — a gross receipts tax applied to virtually all business activity in the state. There is no deduction for expenses, making it a true gross receipts tax. The rates vary by business classification: 0.471% for retailing, 0.484% for manufacturing/wholesaling/extracting, and 1.5%–1.75% for service businesses and professional services. A small business B&O tax credit reduces liability for businesses with annual income under $125,000.
Washington's Sales and Use Tax has a state rate of 6.5%, with local additions of 0.5%–4%, bringing combined rates to 7%–10.6% (Seattle is 10.35%). Monthly returns are due by the 25th. Washington has no corporate income tax, no franchise tax, and no inventory tax. However, the B&O tax on gross receipts can be significant for high-revenue, low-margin businesses. Employers don't withhold income tax but must contribute to Unemployment Insurance and the state's Paid Family & Medical Leave program (employer + employee premiums).
What Happens If You Miss a Washington Tax Deadline?
For B&O Tax and Sales Tax, a late filing penalty of 5% of the tax due applies if the return is 1 month late, increasing to 15% if 2 months late, and 25% if 3+ months late. A minimum penalty of $5 applies.
Interest on unpaid taxes accrues at 1% per month (12% per year) from the original due date. For the Capital Gains Tax, penalties follow the same structure as other excise taxes.
Washington does not offer extensions for B&O or sales tax filings — returns and payments are due on the scheduled date. For the Capital Gains Tax, an extension may be requested by filing the appropriate form by April 15. Failure to file the Annual Report by the due date may result in administrative dissolution. The Department of Revenue may also revoke your business license for persistent noncompliance.
Washington Department of Revenue
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