Key Takeaways
- The failure-to-file penalty (5% of unpaid tax per month, up to 25%) is ten times steeper than the failure-to-pay penalty (0.5% per month) - always file or request an extension on time, even if you can't pay.
- A tax extension only extends your time to file, not your time to pay. You still owe at least 90% of your tax bill by the original April deadline to avoid the failure-to-pay penalty.
- If you file more than 60 days late, the minimum failure-to-file penalty for 2026 returns is $525 or 100% of your unpaid tax, whichever is smaller.
- When both penalties apply in the same month, the failure-to-file penalty is reduced by the failure-to-pay penalty amount, so you're never charged the full 5.5% combined rate.
- Filing something - even an extension you can't fully pay - is always cheaper than filing nothing at all.
If you’re past the tax deadline and haven’t filed, the single most important thing to know is this: filing late costs far more than paying late. Even if you can’t pay your full tax bill, filing your return or an extension on time avoids the harshest IRS penalty.
The Two Penalties, and Why They’re Not Close to Equal
Failure-to-file penalty: 5% of your unpaid tax for each month (or part of a month) your return is late, capped at 25% of the unpaid tax.
Failure-to-pay penalty: 0.5% of your unpaid tax for each month (or part of a month) the balance goes unpaid, also capped at 25%.
The failure-to-file penalty is ten times larger than the failure-to-pay penalty for the same month. That gap is intentional — the IRS wants to know what you owe even if you can’t pay it all right away.
If you file more than 60 days after the deadline (including any extension deadline), a minimum penalty kicks in regardless of how small your balance due is: for 2026 returns, that minimum is $525 or 100% of your unpaid tax, whichever is smaller.
Subscribe or follow us — I’ll update this page each year as the IRS adjusts the minimum failure-to-file penalty for inflation.
What Happens When Both Penalties Apply
If you’re late on both filing and paying in the same month, the IRS doesn’t just stack the two rates. The failure-to-file penalty is reduced by the failure-to-pay penalty for that month — so instead of paying 5.5% combined, you pay 5% total (4.5% failure-to-file + 0.5% failure-to-pay).
This is a small mercy, but the larger lesson holds: filing late is still overwhelmingly the more expensive mistake. Never skip filing just because you can’t pay in full.
The Extension Myth
Here’s the misconception that trips up the most filers: “An extension gives me more time to pay, not just to file.”
That’s not correct. A tax extension (Form 4868) gives you six additional months to file — pushing your deadline to mid-October — but your payment is still due by the original April deadline. If you don’t pay at least 90% of your actual tax liability by then, you’ll owe the failure-to-pay penalty and interest on the shortfall, extension or not.
Four Scenarios and What They Cost You
You filed an extension and paid at least 90% of your bill by the deadline, but didn’t pay the rest by the extended filing deadline. You’ll owe the failure-to-pay penalty (0.5%/month) on the remaining balance, but not the failure-to-file penalty.
You filed an extension but paid less than 90% of your bill by the deadline. You’ll owe the failure-to-pay penalty on the full unpaid balance, continuing to accrue until you pay it off — even after you file your actual return on time under the extension.
You filed an extension, paid at least 90%, but never actually filed your return by the extended deadline. You’ll owe the failure-to-file penalty — 5% per month, up to 25%, with the $525-or-100%-of-tax minimum kicking in past 60 days late.
You did nothing — no extension, no return, no payment. You’ll owe both penalties, calculated together as described above, plus interest that compounds daily on the unpaid balance.
What You Should Actually Do
If you can still prepare and file a complete return, do that rather than requesting an extension — it’s one less step and stops the failure-to-file clock immediately. Tax preparation software and most paid preparers can e-file same-day.
If you genuinely need more time to gather documents, file Form 4868 for an automatic six-month extension — but pay as much of your estimated bill as you can when you file it. The penalty calculations are based on your unpaid balance, so even a partial payment reduces what accrues.
If you’ve already missed the deadline entirely, file now regardless. The failure-to-file penalty keeps growing every month you wait, and there’s no advantage to delaying further once you’ve already missed the original date.
If you can’t pay what you owe even after filing, look into an IRS installment agreement rather than simply not paying — it stops collection action and can reduce the failure-to-pay rate in some cases. For debts you’re confident you can’t ever fully repay, an Offer in Compromise may let you settle for less than the full balance.
Common Issues to Watch Out For
Assuming an extension covers your payment too. It only extends your filing deadline — your payment is still due on the original date, and the failure-to-pay penalty applies regardless of whether you filed an extension.
Waiting to file because you can’t pay in full. This is the single costliest mistake — the failure-to-file penalty is ten times the failure-to-pay rate, so filing an incomplete payment is always better than not filing at all.
Forgetting state extensions are separate. A federal extension doesn’t automatically extend your state filing deadline — check your state tax refund and filing guidance separately.
Not accounting for interest on top of penalties. Interest accrues daily on unpaid tax and compounds, separate from and in addition to both penalties — the IRS adjusts the rate quarterly based on the federal short-term rate.
Assuming a small balance means a small penalty. The 60-day minimum penalty ($525 or 100% of tax owed, whichever is smaller) can apply even to relatively small tax bills, so don’t assume a modest balance due means filing late is low-risk.
