Filed late? Paid late?
Find out what the IRS will charge you.
Free penalty & interest calculator for individuals, C corporations, S corporations, and partnerships — late filing, late payment, estimated tax, and accuracy penalties, built on official IRS rates current through Q3 2026. No signup. Your numbers never leave your browser.
Pick who the return is for, enter your numbers, and hit Calculate — you'll get each penalty, interest, and a month-by-month breakdown.
Estimated balance owed to the IRS
$0
See the month-by-month breakdown
Penalties
| Period | Penalty | Rate | Amount |
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Interest
| Period | Days | Annual rate | Interest |
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Penalty by installment
| Quarter | Due date | Shortfall | Penalty |
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Simple (non-compounded) interest at the quarterly IRS rate — IRC §6654/§6655. Assumes no quarterly estimated payments were made; any you did make reduce each installment's shortfall.
Estimate only — assumes one payment in full and no prior payments, abatements, or IRS notices. Your actual balance is determined by the IRS. This is not tax advice.
How the IRS calculates what you owe
Late-filing penalty
5% per month
Charged on unpaid tax for each month — or part of a month — a 1040 or 1120 is late, up to 25%. Drops to 4.5% in months when the late-payment penalty also applies. File 60+ days late and a minimum penalty kicks in ($525 for returns due in 2026). S corps and partnerships pay per owner instead: $255 per partner or shareholder per month in 2026, up to 12 months — even when no tax is owed.
IRC §6651(a)(1) · §6698 · §6699
Late-payment penalty
0.5% per month
Charged on unpaid tax for each month — or part of a month — from the original due date until you pay, up to 25%. An extension to file does not delay this one: payment was still due with the original deadline.
IRC §6651(a)(2)
Interest
7% per year, right now
The federal short-term rate plus 3 points, set each quarter and compounded daily on your unpaid balance — and on late-filing and accuracy penalties from the return's due date. Unlike penalties, interest has no cap and generally can't be waived.
IRC §6601, §6621
Common questions
I can't afford to pay. Should I still file on time?
Yes — always. The late-filing penalty (5%/month) is ten times the late-payment penalty (0.5%/month). Filing on time and paying late is far cheaper than filing late, and the IRS offers payment plans that also cut the late-payment penalty rate in half while active.
Does a tax extension stop penalties?
Only the late-filing penalty, and only if you file by the extended deadline. An extension gives you more time to file, not to pay — the late-payment penalty and interest still run from the original due date on anything you didn't pay by then.
How do penalties work for S corporations and partnerships?
Differently: because the income passes through to the owners, the late-filing penalty is a flat dollar amount per owner, per month — $255 per partner or shareholder per month for returns due in 2026, for up to 12 months — and it applies even if the business owes no tax. A 10-partner partnership filed one year late faces $30,600. Relief is often available: first-time abatement, and reasonable-cause relief for small partnerships under Rev. Proc. 84-35.
How does the estimated-tax penalty work?
Federal tax is pay-as-you-go: you're expected to pay through withholding or quarterly installments during the year. If you paid less than your "required annual payment" — the smaller of 90% of this year's tax or 100% of last year's (110% if your AGI topped $150,000; corporations use 100%/100%) — each quarterly shortfall is charged simple interest at the IRS underpayment rate until it's paid or the April deadline arrives. Uneven income? The annualized-income method on Form 2210 can shrink the penalty — this calculator uses the standard method.
What is the accuracy-related penalty?
A 20% penalty on tax understated through negligence or a substantial understatement (IRC §6662) — the penalty behind most audit and CP2000 assessments. Worse, interest on it runs from your original return due date, not from when the IRS finds it, so a three-year-old understatement arrives with years of interest attached.
Can I get penalties removed?
Often, yes. If you've filed and paid on time for the past three years, you may qualify for first-time penalty abatement with a single phone call. "Reasonable cause" relief (serious illness, disaster, bad professional advice) is also available. Interest, however, generally can't be removed unless the underlying penalty is.
What interest rate does the IRS charge?
The federal short-term rate plus 3 percentage points, adjusted quarterly and compounded daily. For July–September 2026 it's 7% per year. This calculator applies the correct historical rate to each quarter your balance was outstanding. (Corporate underpayments over $100,000 can draw "hot interest" — 2 points higher — after an IRS notice.)
How accurate is this estimate?
It follows the same rules the IRS uses (IRC §6651, §6654, §6655, §6662, §6601) and official IRS interest rates, assuming calendar-year returns and a single payment in full. Real accounts can differ — partial payments, installment agreements, levy notices, and abatements all change the math. Treat this as a close estimate, not a bill; the IRS's own figure controls.
Is my information stored?
No. The math runs entirely in your browser — the numbers you type are never sent to us or anyone else. See our privacy policy.