Business Tax Deadlines

State filing information

Washington

Business tax filing in Washington: state returns, sales tax, other business taxes, and the federal dates that apply everywhere.

checked 2026-09-01Verified against Washington State Department of Revenue. 13 sources.

Corporate income tax return

None
Washington imposes no corporate (or individual) income tax

Partnership / S corporation returns

Not confirmed
No state income tax return for partnerships or S corporations (no income tax)

Sales tax return

25th of the following month
retail sales and use tax · DOR assigns the filing frequency based on the business's estimated annual tax liability (all taxes on the Excise Tax Return combined)

Other business taxes

1 tax
Business & Occupation (B&O) tax (gross receipts tax)

Washington State Department of Revenue

Other business taxes

TaxWho owes itDue
Business & Occupation (B&O) tax (gross receipts tax)Most businesses conducting business in Washington, regardless of entity type; measured on gross income/gross proceeds with no deduction for costsReported and paid on the same combined Excise Tax Return as sales tax, on the DOR-assigned frequency:...

Rules in full

Corporate income tax

Washington imposes no corporate (or individual) income tax. Businesses instead pay the Business & Occupation (B&O) gross receipts tax, reported on the combined Excise Tax Return (see other_business_taxes). Note: Washington's 7% capital gains excise tax applies to individuals only (individuals can be liable through ownership of a pass-through entity); it is filed by the individual's federal return due date (typically April 15). DOR's income tax page also states that beginning Jan. 1, 2028 a new 9.9% income tax will apply to individuals with AGI over $1 million (enacted 2025 session).

Partnerships and S corporations

No entity-level income tax and no PTE election (nothing to work around). B&O is itself an entity-level gross receipts tax owed by all entity types.

Retail sales and use tax

Due date. Monthly returns are due the 25th of the following month; quarterly returns are due the last day of the month following the quarter (Apr 30, Jul 31, Oct 31, Jan 31); annual returns are due April 15 of the following year. If the due date falls on a weekend or legal holiday it moves to the next business day.

Filing frequency. DOR assigns the filing frequency based on the business's estimated annual tax liability (all taxes on the Excise Tax Return combined); DOR may change it based on actual reporting.

Thresholds. Annual: annual tax liability $1,050 or less. Quarterly: $1,051 - $4,800. Monthly: $4,801 or more.

Prepayments. None. No accelerated or prepayment schedule for large filers appears on DOR's filing-frequency pages or in Avalara's Washington guide.

Annual report

Due State business license renewal (not the Secretary of State annual report):... (Washington State Department of Revenue, Business Licensing...)

Notes

The annual Excise Tax Return due date is April 15 (DOR moved it from January 31 to align with federal filing); several third-party guides (Avalara, SalesTaxHandbook) still show January 31/January 25 and are stale. Sales tax and B&O are one combined return with one due date.

What we could not confirm. Avalara and SalesTaxHandbook disagree with DOR on the annual return due date (they say Jan 31/Jan 25; DOR pages say April 15, and DOR's 2026 calendar lists the 2026 annual return as due April 15, 2027) - DOR treated as authoritative. Exact year DOR changed the annual due date was not confirmed from an official page. Frequency thresholds ($1,050 / $4,800) come from a single DOR page; no secondary source restates the dollar amounts. Business-license renewal expiration dates vary per business (printed on the license), so no single calendar date. Capital gains tiered-rate change referenced on the DOR page was not verified in detail.

Active IRS disaster relief in Washington

Taxpayers in the declared areas below have federal deadlines postponed. The IRS release governs who qualifies.

  1. FEB1Mon
    Washington
    Wildfires in Douglas County Washington
    Postponed to
  2. FEB1Mon
    Washington
    Wildfires in Washington
    Postponed to

All active postponements

Federal dates that apply in Washington

  1. SEP15Tue
    Individuals & Sole Proprietors
    Q3 2026 estimated tax payment (Form 1040-ES)
  2. SEP15Tue
    Partnerships
    Form 1065 extended return (Form 7004), tax year 2025
  3. SEP15Tue
    S-Corporations
    Form 1120-S extended return (Form 7004), tax year 2025
  4. SEP15Tue
    C-Corporations
    Q3 2026 corporate estimated tax (Form 1120-W)
  5. OCT15Thu
    Individuals & Sole Proprietors
    Form 1040 extended return (Form 4868), tax year 2025
  6. OCT15Thu
    C-Corporations
    Form 1120 extended return (Form 7004), tax year 2025

All 2026 federal deadlines

Sources

  1. https://dor.wa.gov/ official
  2. https://dor.wa.gov/file-pay-taxes/filing-frequencies-due-dates official
  3. https://dor.wa.gov/taxes-rates/income-tax official
  4. https://dor.wa.gov/taxes-rates/business-occupation-tax official
  5. https://dor.wa.gov/taxes-rates/other-taxes/capital-gains-tax official
  6. https://dor.wa.gov/file-pay-taxes/filing-frequencies-due-dates/2026-excise-tax-return-due-dates official
  7. https://dor.wa.gov/manage-business/run-business/get-or-renew-your-business-license official
  8. https://dor.wa.gov/open-business/business-licensing-and-renewals-faqs official
  9. https://dor.wa.gov/forms-publications/publications-subject/tax-topics/2025-tax-legislation official
  10. https://taxfoundation.org/data/all/state/state-corporate-income-tax-rates-brackets/
  11. https://www.taxjar.com/sales-tax/washington
  12. https://www.avalara.com/us/en/taxrates/state-rates/washington/washington-sales-tax-guide.html
  13. https://www.salestaxinstitute.com/resources/business-and-occupation-rates-set-to-increase-with-washington-house-bill-2081

Checked 2026-09-01; researcher confidence 0.90. Corrections with a link to the state's own page: contact@businesstaxdeadlines.com.