Full 2026 Tax Year Timeline
Work out your quarterly estimated tax payment.
Use the Self-Employment Tax Calculator →Business Filing Deadlines
If you run a business, your federal filing deadline depends on your entity structure:
- 15 March — S-corporations (Form 1120-S) and partnerships (Form 1065)
- 15 April — C-corporations (Form 1120) and sole proprietorships (filed with your personal Form 1040, Schedule C)
- 16 September — extended deadline for S-corps and partnerships that filed for an extension in March
- 15 October — extended deadline for C-corps that filed for an extension in April
Who Needs to Make Quarterly Estimated Payments?
If your income isn't fully covered by withholding — most commonly because you're self-employed, a freelancer, or have significant investment or rental income — you're generally required to make quarterly estimated tax payments if you expect to owe at least $1,000 in tax for the year. This isn't optional bookkeeping; skipping it can trigger an underpayment penalty even if you pay everything owed by April.
A common safe harbor: paying at least 90% of your current year's tax liability, or 100% of last year's liability (110% if your prior-year AGI was over $150,000), spread across the four quarterly payments, generally protects you from the underpayment penalty.
What an Extension Actually Does (and Doesn't Do)
This is the single most misunderstood part of the US tax calendar: Form 4868 extends your time to file, not your time to pay. If you owe tax, it's still due by the original April deadline — filing an extension without paying an estimated amount just means interest and the Failure to Pay penalty start accruing immediately, even though you technically won't be in trouble for filing late.
The practical move: estimate what you owe as accurately as you can, pay that amount by the April deadline alongside your extension request, then use the extra six months to actually finish your paperwork properly.
Penalties for Filing or Paying Late
| Penalty | Rate |
|---|---|
| Failure to File | 5% of unpaid tax per month (or part of a month), up to 25% total |
| Failure to Pay | 0.5% of unpaid tax per month (or part of a month), up to 25% total |
| Both apply in the same month | Failure to File penalty is reduced by the Failure to Pay amount that month, so the combined rate stays at 5%/month |
| Filing more than 60 days late | Minimum penalty applies — the smaller of a fixed dollar amount or 100% of the unpaid tax |
The takeaway: failing to file is far more expensive than failing to pay, dollar for dollar. Even if you can't pay what you owe, always file on time (or file an extension) to avoid the steeper Failure to File penalty.
State Deadlines Often Differ
Many states align their individual income tax deadline with the federal 15 April date, but not all do, and state extension rules don't always mirror federal ones. If you owe state tax, check your specific state's department of revenue — don't assume federal and state deadlines and extension rules are identical.
Frequently Asked Questions
Deadlines shift to the next business day when they fall on a weekend or federal holiday, and Washington D.C. Emancipation Day (April 16) can push the April deadline back a day or two in some years. Always confirm current dates on IRS.gov.