Free Tool
IRS Penalty and Interest Calculator
Updated
Estimate what the IRS is adding to your tax bill — the failure-to-file penalty, the failure-to-pay penalty, the accuracy-related penalty, and daily interest at the current IRS rate. Enter your actual dates for a closer figure. It runs privately in your browser; nothing is saved or sent.
How it works: the IRS charges 5% per month to file late (4.5% when the pay penalty also applies), 0.5% per month to pay late (1% after a notice of intent to levy), a 20% accuracy penalty when it applies, and daily interest — currently 7% a year (the rate resets quarterly). Fill in your details below for an estimate.
Verified against the IRS's own rules and professional tax software. Built on the current IRS penalty rules and interest rate, and checked side-by-side against the figures professional tax software produces. It's still an estimate, the IRS uses your exact dates, but the math is the real thing.
Estimated total you'd owe
$0
This is an estimate only, not a bill. The IRS applies your exact figures, resets the interest rate each quarter, and charges interest on the penalties too, so your real number can differ. Use it to understand the shape of what you owe, then confirm with a professional.
Penalties Adding Up? You May Be Able to Remove Them.
Many of these penalties qualify for first-time or reasonable-cause abatement. We'll review your case free, tell you honestly what's removable, and map the fastest way to stop the bleeding.
How IRS penalties and interest stack up
Three separate charges pile onto a late tax bill. The failure-to-file penalty is the big one: 5% of the unpaid tax every month, maxing out at 25% after five months. The failure-to-pay penalty is smaller but lasts longer, 0.5% a month up to 25%, and it keeps running for years. When both apply in the same month the IRS caps the combined rate at 5%, so the file penalty drops to 4.5%. A separate accuracy-related penalty of 20% can apply if the IRS decides you understated the tax. On top of it all, interest compounds daily at the federal short-term rate plus 3 points, currently 7% a year for the quarter beginning July 1, 2026, reset every quarter, and it accrues on the penalties as well as the tax.
The good news: penalties are often removable. If you have a clean compliance history you may qualify for First-Time Abatement, and life events (illness, disaster, lost records) can support reasonable-cause relief. Interest generally can't be abated unless it relates to an IRS error, which is why stopping the penalties and the underlying balance quickly matters. If you can't pay in full, an installment agreement at least halves the pay penalty, and an offer in compromise may settle the whole thing.
IRS penalties and interest side by side
What the IRS can charge on an unpaid balance, at what rate, and where each one stops.
| Charge | Rate | Maximum | What changes it |
|---|---|---|---|
| Failure to file | 5% of the unpaid tax for each month or part of a month the return is late | 25% | Reduced to 4.5% in any month the failure-to-pay penalty also applies, so the combined charge is 5% per month |
| Failure to pay | 0.5% of the unpaid tax for each month or part of a month the tax is unpaid | 25% | Drops to 0.25% per month on an approved installment agreement; rises to 1% per month after a notice of intent to levy |
| Accuracy-related | 20% of the portion of the underpayment caused by negligence or a substantial understatement of tax | — | Charged on top of any failure-to-file or failure-to-pay penalty when the IRS applies it |
| Interest | Federal short-term rate plus 3 percentage points, compounded daily | — | Reset every quarter, and it accrues on the penalties too. For the quarter beginning July 1, 2026 the rate is 7% per year |
The interest rate is reset quarterly, so check the current quarter before relying on a figure. Whether any penalty can be reduced or removed depends on your own facts and circumstances.
The types of penalties this covers, and the ones it doesn’t
This tool models the two charges that land on almost every late tax bill, failure-to-file and failure-to-pay, plus the daily interest running underneath both. Once a balance is assessed the IRS will send you a notice, usually a CP14, showing tax, penalties and interest as of the print date. If a notice or letter has already arrived, start from the amount you owe on it; the estimate here picks up where that figure leaves off.
Two types of penalties are deliberately left out. The penalty for underpaid estimated tax payments runs on its own formula, quarter by quarter on Form 2210, and folding it into this arithmetic would produce a wrong number. The accuracy-related penalty at 20% exists only once the IRS asserts it, usually after an audit, so there is nothing to compute in advance. If either applies to you, the real total is higher than the estimate.
What this estimate can’t tell you
Any online calculator, including this one, works from the published formulas. The IRS computes interest on exact daily factors tied to your account’s own transaction dates, so its figure and an estimate will usually differ by a small amount even when every input is right.
Three things no estimator can see:
- Unassessed penalties. Until the IRS actually assesses a penalty it does not exist on your account. Audit adjustments and the 20% accuracy-related penalty are the common ones. A calculator cannot include a penalty nobody has charged yet.
- Your account’s real dates. Payments, credits, extensions and prior notices all move the arithmetic. The IRS applies them on the dates they posted, which is rarely the date you remember.
- State tax. Oklahoma, California and every other state run their own penalties and interest on their own schedules. Nothing here touches them.
If you want the exact number rather than a close one, it is on your IRS account transcript, and it is free. The estimate is for deciding whether this is a problem worth acting on.
IRS interest calculator: what the interest actually costs
Interest is the half people forget, and it behaves differently from the penalty. The IRS sets the underpayment rate every quarter rather than fixing it for the year. For the fourth quarter of 2026 it is 7%. In the third quarter it was 6%. Checked against IRS.gov on 8 September 2026, and worth re-checking if you are reading this later, because that number moves.
The part that matters for planning: a payment plan does not stop interest. It keeps running on whatever is still unpaid, for as long as it is unpaid. What a plan changes is the penalty rate, not the interest rate.
So the two numbers on this calculator move for different reasons. The penalty is partly in your hands, because filing on time and getting a plan approved both change it. The interest is not negotiable and is not reduced by cooperating. That is why paying down principal earlier beats almost any other move once a plan is in place.
Late payment penalty: what it costs if you filed on time but paid late
This is the most common situation we see, and it is the cheapest one to be in. Filing on time and paying late carries the failure-to-pay penalty, which is 0.5% of the unpaid tax for each month or part of a month it stays unpaid, and it stops at 25% of what you owe.
Three things change that rate, and two of them are in your control:
- An approved payment plan cuts it to 0.25% a month, if you filed the return on time. Half rate, and the balance does not have to be paid off for it to apply.
- It rises to 1% a month if the tax is still unpaid 10 days after the IRS sends a notice of intent to levy.
- The charge is applied in full monthly increments, even if you pay the balance before the month ends. There is no proration, so paying early in a month costs the same as paying late in it.
All four figures were checked against IRS.gov on 8 September 2026.
What this tool is, and what it is not
Used as an IRS penalty calculator it estimates the failure-to-file and failure-to-pay charges on a balance. Used as an IRS interest calculator it is necessarily an approximation, and it is worth knowing why. How much interest does the IRS charge is not a fixed number: the rate is the federal short-term rate plus three percentage points, it is reset quarterly, and it compounds daily. Any figure produced before your account is actually assessed is an estimate, not a bill.
Common questions
How much is the IRS failure-to-file penalty?
The failure-to-file penalty is 5% of the unpaid tax for each month or part of a month your return is late, up to a maximum of 25%. When the failure-to-pay penalty also applies in the same month, the failure-to-file penalty is reduced to 4.5%, so the combined penalty is 5% per month. If the return is more than 60 days late, a minimum penalty applies.
How much is the IRS failure-to-pay penalty?
The failure-to-pay penalty is 0.5% of the unpaid tax for each month or part of a month the tax is unpaid, up to a maximum of 25%. It drops to 0.25% per month while you are on an approved installment agreement, and rises to 1% per month after the IRS issues a notice of intent to levy.
What is the IRS accuracy-related penalty?
The accuracy-related penalty is 20% of the portion of the underpayment caused by negligence or a substantial understatement of tax. It is charged on top of any failure-to-file or failure-to-pay penalties when the IRS applies it.
How much interest does the IRS charge?
For individuals, the IRS interest rate on unpaid tax is the federal short-term rate plus 3 percentage points, compounded daily. For the quarter beginning July 1, 2026 that rate is 7% per year. The rate is reset every quarter, and interest also accrues on the penalties.
What do I need to estimate IRS penalties and interest?
You need the tax year, the original tax owed for that year, the return's original due date, the date the return was filed or will be filed, the date you expect to pay, and any payments or withholding already applied. Missing any of those changes the result, and the payment dates matter more than people expect because interest compounds daily.
How accurate is an online IRS penalty and interest calculator?
Close, but not exact. Calculators use the published formulas, while the IRS computes interest on exact daily factors tied to your account's own transaction dates. An estimate also cannot include penalties the IRS has not assessed yet, such as audit adjustments or the 20% accuracy-related penalty, and it does not cover state tax. For the exact figure, check your IRS account transcript.
Clarity Tax Relief is not affiliated with the IRS or any government agency. This calculator is general information, not individualized tax or legal advice; exact penalties, interest, and eligibility depend on individual facts, and no outcome is guaranteed.
More tools: Offer in Compromise Calculator · CSED Calculator · IRS Help Center. Reviewed by Melissa Ly, Chief Tax Officer.
How to use this IRS penalty and interest calculator
Use it as an IRS penalty calculator when a return went in late, or as an IRS interest calculator when the question is how much a sitting tax debt grows by the month. Either way, a tax penalty calculator is only as good as the dates you give it, so have the filing date and any payment dates to hand before you start.
- Enter the unpaid tax only, since penalties are calculated on the tax rather than on the running total.
- Enter the original due date and the date the return was actually filed, because filing late and paying late are separate penalties.
- Note that a partial month counts as a whole month for both penalties.
- Check the First Time Abate condition before assuming the penalties are fixed.
“The failure to pay penalty is 0.5% of the unpaid taxes for each month or part of a month the tax remains unpaid.”
— IRS, Failure to pay penalty
The passage quoted above is from IRS, Failure to pay penalty.