To calculate the failure-to-file penalty, multiply your unpaid tax by 5% for each month or partial month your return is late, up to a maximum of 25%. If the return arrives more than 60 days after the deadline, compare that figure to a minimum penalty of $525 (for returns due in 2026) or 100% of the unpaid tax, whichever is less, and pay the higher of the two amounts. The penalty only exists when you actually owe tax, so the calculation starts with pinning down three numbers: what you owe, when it was due, and how late you filed.
The Three Numbers You Need
Your unpaid tax is the base the penalty runs on, not your income or your total tax liability. On Form 1040, that’s line 37, “Amount you owe.” You can also work backward from line 24 (total tax) by subtracting withholding on line 25, estimated payments on line 26, and any refundable credits. If the result is zero or negative, stop. There is no failure-to-file penalty.
Your deadline for most individual returns is April 15, 2026. A timely Form 4868 pushes the filing deadline to October 15, but only the filing deadline. The clock for interest and the failure-to-pay penalty still starts April 15 on anything you haven’t sent in.
Your months late is the gap between that deadline and the date the IRS received the return. Any fraction of a month counts as a full month. One day late is one month. Thirty-one days late is two.
The 5% Per Month Rule
Federal law sets the failure-to-file penalty at 5% of your unpaid tax for each month or partial month the return is outstanding, with a ceiling of 25%. The cap is reached at five months, and after that the filing penalty stops growing.
The base is what you still owed as of the filing deadline. Withholding, estimated payments, and money sent with an extension request all shrink that base before you multiply. Owe $8,000 on paper but had $6,000 withheld? The penalty runs on $2,000.
The $525 Minimum for Returns Over 60 Days Late
Once a return crosses the 60-day mark, a floor kicks in. For returns due after December 31, 2025, the minimum penalty is the lesser of $525 or 100% of the unpaid tax. The IRS adjusts the dollar figure for inflation periodically.
You apply the minimum only if it beats the percentage calculation. Owe $300 and file four months late, and the percentage math gives you $60 (4 × 5% × $300). But the return is past 60 days, so you check the minimum: the lesser of $525 or $300 is $300. You pay $300, not $60. On a small balance filed very late, this floor is what does the damage.
What Happens When You Also Paid Late
Most late filers also missed the payment deadline, which triggers a separate failure-to-pay penalty of 0.5% per month. To keep the combined monthly hit at 5%, the IRS reduces the filing penalty by the payment penalty during any overlapping month. In practice, you pay 4.5% per month for failing to file and 0.5% per month for failing to pay.
The offset runs for the first five months. After the filing penalty tops out (22.5% after the reduction, plus 2.5% in concurrent payment penalties, totaling the 25% cap), the failure-to-pay penalty keeps going alone at 0.5% per month up to its own 25% ceiling. A taxpayer who never files and never pays can eventually face 47.5% in combined penalties on the original balance, before interest.
Two Worked Examples
Example one: you owe $10,000 and file three months late, having paid nothing.
- Filing penalty: 4.5% × $10,000 × 3 months = $1,350
- Payment penalty: 0.5% × $10,000 × 3 months = $150
- Combined: $1,500
The 25% cap on the filing penalty is $2,500, so $1,350 is well under. The return isn’t more than 60 days late, so the $525 minimum doesn’t apply. Total penalty: $1,500, plus interest.
Example two: you owe $400 and file 90 days late. The percentage calculation gives you $60 (3 × 5% × $400). But 90 days is past 60, so check the minimum. The lesser of $525 or 100% of $400 is $400. Your penalty is $400.
If the IRS Determines the Failure Was Fraudulent
A fraudulent failure to file triples the rate. Instead of 5% per month, it runs at 15% per month, and the cap rises from 25% to 75%. On a $10,000 balance, that hits its $7,500 maximum in five months. The IRS carries the burden of proving fraud, but the multiplier is worth knowing exists.
When the Penalty Is Zero
Because the calculation is a percentage of unpaid tax, filing late when you’re owed a refund produces no penalty. You do, however, lose the refund itself if you wait too long: the general limit is three years from the original due date. Refundable credits like the Earned Income Credit are only paid if you file, and the same three-year window applies.
Interest Runs Separately
The penalty isn’t the whole cost. Interest on unpaid tax accrues from the original due date and also attaches to unpaid penalties. For the first quarter of 2026, the individual underpayment rate is 7% per year, compounded daily. On a $10,000 balance, that’s roughly $1.92 per day. The IRS resets the rate quarterly, and interest generally can’t be waived; it runs until tax, penalty, and accrued interest are all paid.
Getting the Penalty Removed
The calculation gives you the amount on the notice. It isn’t always the amount you end up paying. Two forms of relief can wipe the failure-to-file penalty out.
First Time Abate
If you filed all required returns for the three tax years before the penalty year, received no penalties during that period (or had any prior penalty removed for a reason other than First Time Abate), and have paid or arranged to pay any current tax due, the IRS will often waive the penalty administratively. You don’t have to prove hardship. Call the number on the notice, and the representative can frequently approve it on the spot.
Reasonable Cause
If First Time Abate isn’t available, you can request relief by showing reasonable cause. The IRS accepts serious illness, natural disasters, destruction of records, death in the immediate family, and system outages that blocked timely electronic filing. Explain what happened, when, and why it specifically kept you from filing on time. If the request can’t be handled by phone, submit Form 843 with supporting documentation. Both spouses must sign if it relates to a joint return.
Filing the return, even without payment, stops the failure-to-file penalty from growing. That’s the single most useful move once you know you’re late: get the return in, then work on the balance and any relief request from there.