Tax Extension Deadline Penalty Calculator
Failure-to-file track
Starts Oct 15, 2026 (the extension deadline)
The $525 minimum penalty rule applies here (more than 60 days late).
Failure-to-pay track
Starts Apr 15, 2026 (the original deadline — extension doesn't move this)
This estimate does not include the IRS's same-month combined-penalty offset (failure-to-file is reduced by failure-to-pay in months where both apply) or interest charges. For your exact bill, consult the IRS or a tax professional.
Free calculator that separates the two different IRS penalties people conflate after missing the Oct 15, 2026 tax extension deadline: failure-to-file (5%/month from Oct 15) and failure-to-pay (0.5%/month from the original Apr 15 deadline) — plus the $525 minimum penalty rule for returns more than 60 days late.
How it works
- Enter your unpaid tax amount
- Enter the date you filed (or will file) your return
- Enter the date you paid (or will pay) the tax owed
- See two clearly separated penalty tracks — failure-to-file (starts Oct 15) and failure-to-pay (starts Apr 15) — plus the combined estimate
Frequently asked questions
Does the Oct 15 extension deadline give me more time to pay?
No. An extension only gives you more time to file your return — the original Apr 15 deadline for paying any tax you owe still applies, and failure-to-pay penalties accrue from that date regardless of whether you filed an extension.
What's the difference between failure-to-file and failure-to-pay penalties?
Failure-to-file is 5% of your unpaid tax per month (or part of a month) your return is late, up to 25%, measured from the extended Oct 15 deadline. Failure-to-pay is a separate, smaller 0.5% per month, up to 25%, measured from the original Apr 15 deadline — the two run independently and can overlap.
What is the $525 minimum penalty?
If your return is more than 60 days late, the IRS charges a minimum failure-to-file penalty of whichever is less: $525 (for 2026 returns) or 100% of the unpaid tax. This calculator applies it automatically when it's more than your computed percentage-based penalty.
Does this include IRS interest charges?
No — this tool estimates the failure-to-file and failure-to-pay penalties only, not interest, which the IRS charges separately and compounds daily. It also doesn't apply the IRS's same-month combined-penalty offset. For your exact bill, consult the IRS or a tax professional.
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Update history
- 2026-09-29 Launched: separates failure-to-file (from the Oct 15 extension deadline) and failure-to-pay (from the original Apr 15 deadline) penalty tracks with the 60-day $525 minimum-penalty rule, using verified 2026 IRS figures.