Enter your unpaid tax balance and how long it has been overdue to estimate your failure-to-pay penalty, failure-to-file penalty, and the interest the IRS is adding to your account.
These are two separate penalties, and many taxpayers owe both. The failure-to-pay penalty applies when you don't pay the tax shown on your return by the due date. It accrues at 0.5% of your unpaid balance for each month or part of a month the tax remains unpaid, and it stops growing once it reaches a cap of 25% of the original balance. The failure-to-file penalty is much steeper: it runs at 5% of the unpaid tax per month. Because filing late is treated more seriously than paying late, the IRS wants you to file on time even if you cannot pay in full.
When both penalties apply in the same month, the IRS reduces the 5% failure-to-file penalty by the 0.5% failure-to-pay penalty, so the combined rate is effectively 4.5% per month for the late-filing portion. The failure-to-file penalty is capped at 22.5% of the unpaid tax (after the offset), while the failure-to-pay penalty is capped at 25%. That means a balance that sits unaddressed long enough can accumulate close to 47.5% in combined penalties alone, before any interest is added. This calculator applies the same caps so your estimate does not overstate the penalties once those limits are reached.
On top of penalties, the IRS charges interest on both the unpaid tax and on the penalties themselves. The interest rate is set quarterly — it equals the federal short-term rate plus 3% for most individual taxpayers — and it compounds daily, so the longer a debt is outstanding the faster it snowballs. Our tool uses a simplified 8% annual estimate so you can see the direction and rough magnitude of interest charges. Treat that figure as an approximation, not an exact IRS calculation, because the real rate changes every three months and daily compounding produces a slightly higher number over time.
Penalties are not always permanent. If you have a clean compliance history for the prior three years, you may qualify for First-Time Abatement, which can remove failure-to-file and failure-to-pay penalties for a single tax period. You may also request reasonable-cause relief if circumstances outside your control — serious illness, a natural disaster, the death of a family member, or reliance on incorrect professional advice — kept you from filing or paying on time. Interest is harder to remove and is generally only abated when it was caused by an IRS error or delay.
The single most effective step is to file every required return, even if you cannot pay, because that stops the larger failure-to-file penalty from accruing. Paying down any amount reduces the base on which the failure-to-pay penalty and interest are calculated. Setting up an installment agreement can cut the failure-to-pay rate, and resolving the underlying balance through a payment plan or Offer in Compromise ultimately stops the meter. The sooner you act, the less these charges compound against you.
Moderate — penalty estimates use the statutory rates, but cannot match the IRS's exact account computation with daily, quarterly-adjusted interest.
Last updated: June 2026
This tool provides educational information only. It does not constitute legal advice and should not be relied upon as such. For legal advice regarding your specific situation, consult a licensed attorney.
This tool is for educational purposes only. It does not constitute tax advice. Results are estimates based on general information. For advice specific to your tax situation, consult a qualified tax professional, enrolled agent, CPA, or tax attorney.
See our Methodology and Data Sources for more information.
This content is based on the following authoritative sources. All sources are regularly verified for accuracy.
26 U.S.C. § 6651
26 U.S.C. § 6601, § 6621
Internal Revenue Manual 20.1.1