Missing a tax deadline triggers penalties and interest. Knowing the dates ahead of time lets you plan, file extensions if needed, and avoid surprises. Here's the complete 2026 tax calendar for personal and business filers.
Personal Tax (Form 1040) Deadlines
- April 15, 2026: Individual federal returns due. Also the deadline to file an extension (Form 4868).
- April 15, 2026: If you owe taxes, payment is due THIS DATE — even if you file an extension. Extensions extend filing time, not payment time.
- October 15, 2026: Extended individual returns due.
Quarterly Estimated Tax Payments (2026)
If you're self-employed, have rental income, capital gains, or any income without withholding, you generally need to make quarterly estimated payments to avoid underpayment penalties.
- Q1 2026: April 15, 2026
- Q2 2026: June 16, 2026 (June 15 falls on a Sunday)
- Q3 2026: September 15, 2026
- Q4 2026: January 15, 2027
Business Entity Deadlines
S-Corporations and Partnerships
- March 17, 2026: S-Corp (1120S) and Partnership (1065) returns due. (March 15 falls on a Sunday.)
- March 17, 2026: Last day to file extension (Form 7004) for S-Corps and Partnerships.
- September 15, 2026: Extended S-Corp and Partnership returns due.
C-Corporations
- April 15, 2026: C-Corp (1120) returns due (calendar-year filers).
- April 15, 2026: Last day to file C-Corp extension.
- October 15, 2026: Extended C-Corp returns due.
Fiscal-year C-Corps have different deadlines based on year-end.
Information Return Deadlines (Issuing Forms)
If you have employees or have paid contractors:
- January 31, 2026: W-2s must be issued to employees and filed with SSA
- January 31, 2026: 1099-NEC forms must be issued to contractors and filed with IRS
- February 28, 2026: Other 1099 forms (1099-MISC, 1099-INT, 1099-DIV) due to IRS if filing on paper
- March 31, 2026: Other 1099 forms due to IRS if filing electronically
Payroll Tax Deadlines
- Form 941 (quarterly payroll): April 30, July 31, October 31, January 31
- Form 940 (FUTA annual): January 31, 2026 (for tax year 2025)
- Federal tax deposits: Vary by employer size — semi-weekly or monthly
Washington State Deadlines
Washington has no state income tax, but businesses still have:
- B&O Tax (DOR): Monthly, quarterly, or annual depending on business size — most small businesses file quarterly
- Sales tax: Same schedule as B&O
- Annual report (Secretary of State): Due by your business entity's anniversary date each year — failure to file leads to administrative dissolution
- Workers' comp (L&I): Quarterly
- Unemployment insurance (ESD): Quarterly
HSA, IRA, and Retirement Contribution Deadlines
- Traditional and Roth IRA contributions for 2025: April 15, 2026 (same as tax filing deadline)
- HSA contributions for 2025: April 15, 2026
- SEP-IRA contributions for 2025: Due by tax return due date INCLUDING extensions (October 15 if you extended)
- Solo 401(k) contributions: Same as SEP-IRA
What Happens If You Miss a Deadline
- Failure to file penalty: 5% of unpaid taxes per month, capped at 25%
- Failure to pay penalty: 0.5% per month of unpaid taxes
- Interest: Federal short-term rate plus 3%, compounded daily
- If you file but don't pay: Just the failure-to-pay penalty (much smaller)
- If you don't file at all: Both penalties apply
Bottom line: Even if you can't pay, file the return. The penalty for not filing is 10x worse than the penalty for not paying.
If You're Going to Miss a Deadline
File an extension. Extensions are free, automatic, and give you 6 more months. The only catch: if you owe taxes, you still have to pay the estimated amount by the original deadline. Don't skip the extension to avoid the math — file it, even if you have to estimate.
Need Help With a Filing or Extension?
Pamela Beaton, CPA can prep returns, file extensions, and help you avoid penalties. Call early — the closer to a deadline, the harder it is to get scheduled.
Call 360-435-3440