Late Tax Payment Penalty Calculator
Use this late tax payment penalty calculator to estimate what the IRS adds when you pay your federal tax after the deadline. It combines the failure-to-file penalty (5%/month), the failure-to-pay penalty (0.5%/month) and daily-compounded interest into one clear total.
⚠️ Estimate only — see the disclaimer.
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Estimate your late payment penalty
Enter your details and select Calculate to see your estimated penalty.
What this calculator does
Paying federal tax after the deadline triggers up to three separate charges: the failure-to-file penalty, the failure-to-pay penalty and interest. This calculator combines all three into a single estimate so you can see the real cost of paying late and decide how quickly to act. It works for individual income tax balances (Form 1040) and follows the IRS rules for how the two penalties interact.
The most important takeaway is built into the math: the penalty for filing late is ten times bigger than the penalty for paying late. If money is tight, file (or file an extension) on time and pay whatever you can.
How to use this calculator
- Enter your unpaid tax balance — the amount still owed.
- Set the payment due date (normally April 15) and the date you paid or expect to pay.
- Tick the box if your return was filed late (leave it ticked if unsure and you missed the deadline; untick if you filed on time or filed an extension).
- Enter the current annual interest rate.
- Select Calculate to see the penalties, interest and total. Use Load example or Clear as needed.
Formula and method
Failure-to-pay = 0.5% × unpaid tax × months late (max 25%)
Failure-to-file = 5% × unpaid tax × months late (max 25%)
− 0.5% for each overlapping month
= 4.5% × unpaid tax × months (max 5 months)
Minimum if >60 days late: lesser of $510 or the tax
Interest = unpaid tax × [(1 + rate÷365)^days − 1]
Total = failure-to-file + failure-to-pay + interest
A “month” means any part of a month — being one day late still counts as a full month. The combined failure-to-file and failure-to-pay penalties can reach a maximum of 47.5% of the unpaid tax (22.5% + 25%), and interest continues until the balance is paid in full.
Example calculation
You owe $5,000, the due date was April 15, and you pay on August 15 (4 months late), having also filed late, at a 7% interest rate.
- Failure-to-file: $5,000 × 4.5% × 4 = $900.
- Failure-to-pay: $5,000 × 0.5% × 4 = $100.
- Interest (~7% daily-compounded for ~122 days) ≈ $118.
- Total penalties + interest ≈ $1,118, so you'd pay about $6,118 in all.
Select Load example to run these figures.
How the two penalties compare
| Charge | Rate | Maximum | When it applies |
|---|---|---|---|
| Failure to file | 5% / month (4.5% if also paying late) | 25% | Return filed after the deadline |
| Failure to pay | 0.5% / month | 25% | Tax paid after the deadline |
| Interest | Federal short-term + 3%, compounded daily | No cap | Any unpaid tax or penalty |
Common mistakes to avoid
- Not filing because you can't pay. This is the costliest mistake — file or extend on time regardless.
- Thinking an extension delays payment. It only delays filing; the tax is still due in April.
- Forgetting interest keeps running. Penalties cap out, but interest compounds until you pay in full.
- Not asking for abatement. First-time abatement can wipe out penalties if you usually file and pay on time.
- Ignoring a payment plan. An IRS installment agreement cuts the failure-to-pay rate to 0.25%/month.
Limitations of this calculator
- This is an estimate. The IRS calculates interest with daily compounding on both tax and penalties; this tool compounds interest on the tax only.
- It does not model an installment agreement (which lowers the failure-to-pay rate to 0.25%/month).
- It does not cover state penalties or business-entity penalties, which differ.
- The minimum failure-to-file amount changes yearly; the figure used here reflects a recent year.
Frequently asked questions
What is the penalty for paying taxes late?
The IRS charges a failure-to-pay penalty of 0.5% of the unpaid tax for each month or part of a month it remains unpaid, up to a maximum of 25%. On top of that, interest accrues daily at the federal short-term rate plus 3%. If you also filed your return late, a separate failure-to-file penalty applies.
How much is the failure-to-file penalty?
The failure-to-file penalty is 5% of the unpaid tax per month, up to 25%. In any month where both penalties apply, the failure-to-file penalty is reduced by the 0.5% failure-to-pay penalty, so it effectively becomes 4.5% per month. If your return is more than 60 days late, a minimum penalty applies (the lesser of about $525 for 2026 or 100% of the tax due).
Is it better to file on time even if I can't pay?
Almost always, yes. The failure-to-file penalty (5%/month) is ten times larger than the failure-to-pay penalty (0.5%/month). Filing on time — or filing an extension — and paying what you can stops the bigger penalty from building up.
Does an extension give me more time to pay?
No. An extension to file (Form 4868) gives you until October to file, but the tax is still due on the original deadline. Paying after that date triggers the failure-to-pay penalty and interest.
Can the IRS remove or reduce these penalties?
Possibly. The IRS offers First-Time Penalty Abatement if you have a clean compliance history, and may waive penalties for reasonable cause such as serious illness or a natural disaster. Interest is rarely removed unless it relates to an abated penalty.
How is the interest calculated?
Interest is charged on the unpaid tax (and on unpaid penalties) and compounds daily. The rate is set quarterly at the federal short-term rate plus 3 percentage points — recently around 6%–8% per year (7% in Q1 2026, 6% from Q2 2026).
Is this the same as the underpayment penalty?
No. This page covers paying your final balance late. If you also didn't pre-pay enough during the year, see the IRS underpayment penalty calculator, which can apply in addition to these penalties.
Disclaimer
This calculator provides general estimates for informational purposes only and is not a substitute for professional tax, legal, accounting or financial advice. Rules, rates and thresholds change frequently and vary by individual circumstances. Always confirm figures with the relevant authority or a qualified professional before acting.
Sources & references:IRS — Failure to File Penalty · IRS — Failure to Pay Penalty · IRS — Interest