If you file 3 months late and owe $4,000, you'll pay $670 in total penalties and interest. That brings your total IRS bill to $4,670.
The math
Inputs
| Tax owed | $4,000 |
|---|---|
| Return due | April 15, 2026 |
| Return filed | 3 months late (July 15, 2026) |
| Tax paid in full | 3 months after the due date (July 15, 2026) |
The formula in words
Failure-to-file: 5% of the unpaid tax for each month or part of a month the return is late, up to 5 months (25%). Failure-to-pay: 0.5% of the unpaid tax per month, up to 25%. In a month when both apply, the failure-to-file charge is reduced by the failure-to-pay charge, and the failure-to-pay charge stays the same. Both penalties are charged only on tax that is still unpaid. If the return is more than 60 days late, the failure-to-file penalty is at least $525 (returns due in 2026) or 100% of the tax, whichever is less. Interest: the IRS rate, compounded daily, on the tax and the failure-to-file penalty from the due date until you pay.
Step by step
| Month late | Failure-to-file | Failure-to-pay | Penalties so far |
|---|---|---|---|
| 1 | $180.00 | $20.00 | $200.00 |
| 2 | $180.00 | $20.00 | $400.00 |
| 3 | $180.00 | $20.00 | $600.00 |
| Charged on | Amount | Interest |
|---|---|---|
| Unpaid tax | $4,000 | $61.84 |
| Failure-to-file penalty | $540 | $8.35 |
Result
- Failure-to-file penalty: $540
- Failure-to-pay penalty: $60
- Interest: $70
- Total penalties and interest: $670
- Total to pay the IRS: $4,670
Assumptions
- Nothing was paid before July 15, 2026 and no extension was filed.
- IRS interest compounded daily at the individual underpayment rate (irs.gov quarterly interest rates): 6% from April 15, 2026; 7% from July 1, 2026.
- Interest on the failure-to-pay penalty is left out: it only starts once the IRS bills you for it, so the real total can be a little higher.
- No penalty relief assumed. First-time abatement or reasonable cause can remove penalties (not interest) if you qualify.
- These are estimates that show how the math works, not financial, tax or legal advice. Lenders, card issuers and the IRS can calculate slightly differently.
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What the $670 total means for you
The $670 is the extra cost of filing and paying 3 months late on a $4,000 tax bill. It breaks down into a $540 failure-to-file penalty, a $60 failure-to-pay penalty, and $70 in interest. Your total to the IRS becomes $4,670.
That is a meaningful share of the original tax owed. The failure-to-file penalty is the big driver because it is charged at 5% of the unpaid tax for each month or part of a month the return is late, up to 5 months. Three months at 5% of $4,000 gives the $540 shown here.
The failure-to-pay penalty is smaller: 0.5% of the unpaid tax per month, up to 25%. Three months at 0.5% of $4,000 gives the $60 shown here. In any month when both penalties apply, the failure-to-file charge is reduced by the failure-to-pay charge, and the failure-to-pay charge stays the same. That is why the two penalties do not simply add together month by month.
Interest is separate. It is charged on the tax and the failure-to-file penalty from the due date until you pay, compounded daily at the IRS rate. In this case, that adds $70.
What drives the penalty up or down
The biggest factor is how long the return stays unfiled. The failure-to-file penalty is 5% per month or part of a month, so even a few days into a new month can add another 5% of the unpaid tax. Here, 3 months late means 3 months of that 5% charge, capped at 5 months.
The amount you still owe also matters. Both penalties are charged only on tax that is still unpaid. If you had paid some of the $4,000 before the due date, the penalties would be based on the smaller unpaid amount. In this example, nothing was paid before July 15, 2026, so the full $4,000 was unpaid the whole time.
Interest depends on the IRS rate and how long the balance is outstanding. The rate here is 6% from April 15, 2026, and 7% from July 1, 2026, compounded daily. Interest is charged on the tax and the failure-to-file penalty, not on the failure-to-pay penalty until the IRS bills you for it.
There is also a minimum failure-to-file penalty if the return is more than 60 days late: at least $525 for returns due in 2026, or 100% of the tax, whichever is less. In this case, the $540 failure-to-file penalty is already above that minimum, so the minimum does not change the result.
How you could change the outcome
Using only the numbers here, the most direct way to lower the cost is to reduce the unpaid tax before the due date. If you had paid the $4,000 by April 15, 2026, there would be no failure-to-pay penalty and no interest on the tax. The failure-to-file penalty would still apply if the return was late, but it would be based on the unpaid tax at the time.
Filing earlier also helps. The failure-to-file penalty is charged for each month or part of a month the return is late, up to 5 months. Filing after 1 month instead of 3 months would mean fewer months of that 5% charge. Filing after 2 months would mean 2 months of the charge. The failure-to-pay penalty would also be smaller because it is 0.5% per month.
Paying earlier reduces interest. Interest runs from the due date until you pay, compounded daily. Paying in full on July 15, 2026, as in this example, produces $70 in interest. Paying sooner would mean less interest, but the exact amount would depend on the date and the IRS rate.
Penalty relief is another possibility. First-time abatement or reasonable cause can remove penalties, but not interest, if you qualify. No relief is assumed in this estimate. If you think you might qualify, ask the IRS or a tax professional.
Practical next steps
First, confirm the exact amounts with the IRS. The figures here are estimates that show how the math works. The IRS can calculate slightly differently, and interest on the failure-to-pay penalty is left out because it only starts once the IRS bills you for it. That means your real total could be a little higher than $4,670.
Second, file the return as soon as you can, even if you cannot pay the full $4,000. The failure-to-file penalty is the larger charge, and it keeps growing each month or part of a month the return is late, up to 5 months. Filing stops that clock.
Third, pay what you can. Both penalties are charged only on tax that is still unpaid, so reducing the balance reduces the penalty base. If you cannot pay in full, ask about a payment plan or an offer in compromise. Those options have their own rules and costs, so check with the IRS or a tax professional.
Fourth, keep records of when you filed and paid. If you request penalty relief, you may need to show reasonable cause or a clean compliance history. First-time abatement can remove penalties, not interest, if you qualify.
Finally, remember these are estimates, not financial, tax, or legal advice. Lenders, card issuers, and the IRS can calculate slightly differently. Confirm your specific numbers with the IRS or a tax professional before you rely on them.
Frequently asked questions
Can the failure-to-file penalty be more than $540?
Yes. The failure-to-file penalty is 5% of the unpaid tax for each month or part of a month the return is late, up to 5 months. Here it is 3 months late, so the charge is $540. If the return were later, the penalty would be higher, up to the 5-month cap.
Does paying late affect the failure-to-file penalty?
Both penalties are charged only on tax that is still unpaid. In this example, nothing was paid before July 15, 2026, so the full $4,000 was unpaid the whole time. If you had paid some tax earlier, the penalties would be based on the smaller unpaid amount.
Why is interest $70 and not more?
Interest is charged on the tax and the failure-to-file penalty from the due date until you pay, compounded daily at the IRS rate. Here the rate is 6% from April 15, 2026, and 7% from July 1, 2026. Interest on the failure-to-pay penalty is left out because it only starts once the IRS bills you for it.
Can I get the penalties removed?
First-time abatement or reasonable cause can remove penalties, not interest, if you qualify. No penalty relief is assumed in this estimate. If you think you might qualify, ask the IRS or a tax professional about your options.
Is the $670 total the final amount I will owe?
It is an estimate. The IRS can calculate slightly differently, and interest on the failure-to-pay penalty is left out because it only starts once the IRS bills you for it. Your real total could be a little higher than $4,670. Confirm with the IRS.