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Late Tax Filing & Payment Penalty Calculator
IRS failure-to-file and failure-to-pay penalties, plus interest.
What happened
Two separate IRS penalties — and how they combine
If you owe tax after the filing deadline, two penalties can apply. Failure-to-File is 5% of the unpaid tax for each month (or partial month) your return is late, capped at 25%. Failure-to-Pay is a much smaller 0.5% per month, also capped at 25%. If both apply in the same month — which is common, since most people who file late also pay late — the IRS doesn't just add them together. Instead, the Failure-to-File rate for that month is reduced by the Failure-to-Pay rate, so the combined bite is 5% per month (4.5% + 0.5%), not 5.5%.
Interest on top of penalties
Separately from penalties, the IRS charges interest on unpaid tax from the original due date until it's paid in full. The rate is set quarterly (tied to the federal short-term rate plus 3%) and compounds daily — this calculator uses a flat illustrative annual rate as a simple approximation, clearly not the exact IRS formula. If you're facing a real penalty, the IRS also offers relief programs (like first-time penalty abatement) that this tool doesn't account for.
Not tax advice. Figures use the 2024 federal tax year and are estimates for general education only — every situation is different. Confirm your numbers with a CPA or tax professional, and check the current year's IRS figures, before filing or making financial decisions.
Frequently asked questions
What if I filed for an extension?
An extension to file generally gives you more time to file your return, but it doesn't extend the time to pay — if you owe tax and didn't pay by the original deadline, Failure-to-Pay penalties and interest can still apply even with a valid extension.
Does the penalty keep growing forever?
No — both Failure-to-File and Failure-to-Pay penalties are individually capped at 25% of the unpaid tax. Interest, however, continues to accrue on any remaining unpaid balance until it's paid in full.
Is the interest rate in this calculator exact?
No — it's a simple illustrative annual rate you can adjust. The IRS sets its actual underpayment interest rate quarterly and compounds it daily, which this simplified tool doesn't replicate exactly.
Can penalties be reduced or waived?
Sometimes. The IRS offers relief such as first-time penalty abatement for taxpayers with a clean recent compliance history, and reasonable-cause relief in certain circumstances. A CPA or tax professional can tell you whether you qualify.