This IRS penalty calculator estimates what a late return will cost: the failure-to-file and failure-to-pay penalties with interest on a return that owes tax, the fixed penalty for a late Form 5472, and the per-partner penalty on a late partnership or S corporation return. It is meant for anyone who missed a deadline and wants to see the size of the problem before deciding what to do.
How to use the calculator
- Which return is late? A return with tax due (1040, 1040-NR, 1120), Form 5472 for a foreign-owned LLC, or a partnership or S-corp return (1065, 1120-S).
- Unpaid tax on the return: the balance due after withholding and payments.
- Months filed late (count part of a month as a month): enter 0 if you filed on time or on extension.
- Months the tax has been unpaid: counted from the original due date.
- Year the return was due: sets the minimum penalty and the per-partner amount.
- Number of late Forms 5472 (one per year): for the Form 5472 option.
- Days since the IRS notice, if you got one: for the Form 5472 option.
- Partners or shareholders: for the partnership and S-corp option.
How it is calculated
Return with tax due. Failure to pay is 0.5% of the unpaid tax per month, capped at 25%. Failure to file is 5% per month for up to five months, minus the failure-to-pay amount for the same months. When the return is more than two months late (the calculator’s stand-in for “more than 60 days”), the filing penalty is at least the smaller of $525 (returns due in 2026; $510 in 2025, $535 in 2027) or 100% of the tax. Interest runs at about 7% a year, compounded daily, for the months the tax is unpaid. Sources: failure-to-file penalty, failure-to-pay penalty, quarterly interest rates.
Form 5472. $25,000 per late form, plus $25,000 for each 30 days, or part of 30 days, that the failure continues beyond 90 days after an IRS notice (Form 5472 instructions).
Partnership or S-corp return. $255 per partner or shareholder per month for returns due in 2026 ($245 in 2025, $260 in 2027), for up to 12 months (Rev. Proc. 2025-32).
Worked example with the default inputs
$5,000 of unpaid tax, filed four months late, unpaid for four months, return due in 2026:
| Line | Amount | How |
|---|---|---|
| Failure-to-file penalty | $900.00 | (5% − 0.5%) × 4 months × $5,000 |
| Failure-to-pay penalty | $100.00 | 0.5% × 4 months × $5,000 |
| Interest | $118.03 | about 7% a year, compounded daily, for 4 months |
| Penalties and interest | $1,118.03 | plus the $5,000 of tax |
The minimum penalty does not apply here because $900 is already above $525. Had the same return been filed on time with the tax still unpaid, the total would fall to $218.03. Filing is what stops most of the cost.
Two other cases from the calculator: two late Forms 5472 with 120 days since the IRS notice come to $100,000 ($50,000 initial plus $50,000 continuation). A two-partner Form 1065 filed four months late comes to $2,040.
What this calculator leaves out
- Interest on penalties. The IRS charges interest on most penalties too; the calculator charges it on the tax only.
- Quarterly rate changes. It uses one average rate. In 2026 the rate was 7%, except 6% in the second quarter.
- Payment plans and levy notices, which change the failure-to-pay rate to 0.25% or 1% a month.
- Partial payments made after the due date.
- Other penalties: the estimated tax underpayment penalty, accuracy-related penalties and state penalties such as New Jersey’s.
- Relief. It shows the penalty before any first-time abatement or reasonable cause relief. For Form 5472, only reasonable cause relief is possible.
Form 5472 penalty and how to fix a late filing
The Form 5472 penalty surprises foreign owners of single-member U.S. LLCs because it has nothing to do with tax owed. An LLC with no U.S. income still has to file a pro forma Form 1120 with Form 5472 for every year it has a reportable transaction with its owner, and money the owner puts in or takes out usually counts.
If you missed one or more years, the practical steps are usually:
- File the missing returns. Prepare a pro forma 1120 and Form 5472 for each missed year, with the transactions for that year, and send them to the address or fax line in the instructions. Filing before the IRS sends a notice keeps the continuation penalty from starting.
- Keep the record clean going forward, with each year’s filing made on time or on extension.
- Consider a relief request. First-time abatement (IRS first-time abate) does not apply to the Form 5472 penalty, so relief there depends on showing reasonable cause. Penalty relief requests are filed by the taxpayer or an authorized representative.
We prepare late and past-due returns, including Form 5472 and the pro forma 1120, and the returns that stop failure-to-file penalties from growing. We do not represent clients before the IRS in audits, appeals or collections, and we do not give legal advice; if your case needs representation, we tell you at the first review.
Getting current
See how we handle back taxes and IRS notices for recent unfiled years, and our Form 5472 filing service for foreign-owned LLCs. Other estimates are on our free tax calculators page. If a deadline has passed, book a free 15 to 30 minute consultation and we will look at what can be filed first.