2026 Tax Deadline Calendar

Filing an extension is straightforward — Form 4868 for individuals, Form 7004 for businesses — but the most common mistake is assuming the extension also delays your payment deadline. It does not. An extension grants additional time to submit your completed return, but any tax owed is still due by the original filing date. If you owe $5,000 and file an extension without paying, interest and the failure-to-pay penalty (0.5% per month, up to 25%) begin accruing from April 15.

For individuals, Form 4868 extends the filing deadline from April 15 to October 15 — a full 6-month extension. S-Corps and partnerships that file Form 7004 get an extension from March 15 to September 15. C-Corporations receive an extension from April 15 to October 15.

The failure-to-file penalty is significantly steeper than the failure-to-pay penalty: 5% per month of unpaid tax (up to 25%). If you cannot pay in full, it is almost always better to file on time and set up an IRS installment agreement (Form 9465) than to skip filing entirely. The IRS charges a $31 setup fee for direct-debit installment agreements and allows balances up to $50,000 on a streamlined plan.

Estimated tax payments follow their own schedule and are never extended. Missing a quarterly payment triggers the estimated tax penalty under IRC Section 6654. The penalty rate equals the federal short-term rate plus 3 percentage points, compounded daily. For 2025–2026, this rate has been running near 8% annually.

Most states with an income tax align their filing deadline with the federal April 15 date, but there are notable exceptions. Iowa sets its individual deadline at April 30. Louisiana uses May 15 for individual returns. Virginia follows May 1. Hawaii historically uses April 20. These differences mean multi-state filers must track each state's calendar independently.

State extension rules also vary. Some states (California, New York, Illinois) grant an automatic extension if you file a federal extension, with no separate state form required. Others (Georgia, Ohio, Michigan) require a separate state extension filing. Always confirm your state's specific rules with the state revenue department.

Penalty structures differ widely across states:

• California (FTB) — late-filing penalty of 5% of tax due plus 0.5%/month for late payment; minimum $135 or 100% of tax (whichever is less)
• New York — 5% per month for late filing (up to 25%); 0.5% per month for late payment
• Texas — no individual income tax, but franchise tax returns are due May 15; 5% penalty if 1–30 days late, 10% if 30+ days late
• Florida — no individual income tax; corporate income/franchise tax due April 1 (fiscal year), 10% penalty for late filing

For S-Corps and partnerships, many states impose per-partner or per-shareholder penalties for late filings, mirroring the IRC Section 6698/6699 federal penalty of $235 per partner per month (2025 rate). A 4-member LLC taxed as a partnership that files 3 months late owes $2,820 in federal penalties alone — before state penalties are added.