IRS penalty and interest calculator for Form 1040

Estimate what the IRS may add when an individual Form 1040 is filed or paid late. The calculator separates failure-to-file, failure-to-pay, tax interest, and interest on the filing penalty; follows partial payments; changes the interest rate by quarter; and shows the IRS's new 2026 penalty-relief scenario without promising eligibility.

Individual Form 1040 estimate

Calculate penalties and interest

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Unpaid tax at the original deadline ($) After withholding, estimated payments, timely payments, and refundable credits.

Original payment due date An extension to file normally does not move this date.

Filing deadline that applied Use the valid extended deadline if you had one.

Date filed (or assumed filing date) If still unfiled, use the calculation date. For a late return, use the e-file acceptance date or the IRS receipt date for paper filing—not a late postmark date.

Calculate through Limited to the last verified data refresh: 2026-07-26.

Partial tax payments (optional)

Add payments made after the original deadline. The estimate applies them to tax principal first and leaves assessed penalties and interest unpaid.

+ Add a payment

Advanced failure-to-pay rates (optional)

Leave blank for the standard 0.5% monthly rate. Only enter dates that actually apply to the IRS account; the calculator does not decide eligibility.

Qualifying installment agreement start The 0.25% rate requires an individual return filed on time. Enter it only if the agreement remained effective through the calculation date; ended agreements are not modeled.

Intent-to-levy notice date The engine applies 1% beginning with the first penalty month after the 10-day period.

Estimate IRS charges

Planning estimate for an individual original Form 1040/1040-SR only. Do not enter a Social Security number, name, address, or other personal information. IRS notices, transcripts, relief determinations, and official payoff figures control.

What this IRS tax penalty calculator includes

The default calculation is the common individual case: tax shown on an original Form 1040 remained unpaid after its deadline, the ordinary late-payment rate applies, and no penalty relief has yet been granted. Unlike a generic percentage calculator, this one preserves four separate clocks:

• Failure to file: runs from the filing deadline that actually applied, including a valid extension.
• Failure to pay: normally runs from the original payment deadline, even when the return had an extension to file.
• Tax interest: compounds daily and changes whenever a new quarterly IRS underpayment rate takes effect.
• Penalty interest: the failure-to-file amount is modeled from its filing deadline. Interest on the failure-to-pay penalty is identified but excluded because the IRS starts it from account-specific notice or assessment dates.

Optional dated tax payments reduce later failure-to-pay bases and tax principal without rewriting the original failure-to-file base. Advanced fields can model a qualifying installment-agreement period or the higher rate after an intent-to-levy notice. Leave those fields blank unless the facts actually apply.

Failure-to-file penalty calculation

For an individual Form 1040, the IRS states that the ordinary filing penalty is 5% of unpaid tax for each month or partial month the return is late, up to 25%. One day late therefore counts as a full penalty month. If the 0.5% failure-to-pay charge applies during the same month, it reduces the filing portion: the ordinary combined charge is generally 4.5% for filing plus 0.5% for payment, not 5.5%.

When a return is more than 60 days late, a due-year minimum can replace the smaller ordinary filing result. For a return due in 2026, the monitored minimum is $525, limited to 100% of the unpaid tax. The minimum is not reduced below that floor by the overlapping payment penalty. Because the amount is indexed, the pipeline checks the official table every week instead of leaving one dollar figure hardcoded in page copy forever.

Failure-to-pay penalty calculation

The standard late-payment penalty is 0.5% of tax still unpaid at the start of each penalty month, up to an aggregate 25% of the original unpaid tax. A payment must be made before a penalty month begins to reduce that month's base; one made during the month—or on its first day—does not prorate the full monthly charge and instead reduces later bases. The calculator's optional payment timeline implements that distinction and displays every charged month.

Two advanced rates are available because the IRS publishes them as separate branches. For a timely filed individual return, an approved installment agreement can reduce the monthly rate to 0.25% while it qualifies. After the specified intent-to-levy period, the rate can rise to 1%. The inputs do not decide whether an agreement or notice is legally effective—they only apply the branch to dates the user supplies.

New for 2026: Automatic Exemption from Penalty

The IRS says Automatic Exemption from Penalty (AEP) begins in summer 2026. Beginning with eligible 2025 tax-year original returns, IRS records showing three prior years of timely compliance may prevent covered failure-to-file and failure-to-pay penalties from being assessed. The taxpayer does not apply when AEP is granted automatically; the IRS sends a notice explaining the result.

The calculator keeps the statutory estimate as the primary answer and, for a potentially eligible current return, shows a separate if the IRS confirms AEP comparison. It never declares a user eligible. AEP does not erase the underlying tax or tax interest, and it does not cover every type of penalty. Read the official IRS administrative penalty relief guidance before relying on the comparison.

Why the result is an estimate, not an IRS payoff

An IRS account is an event ledger, not one formula. Notices and assessments determine when interest starts on the failure-to-pay penalty; payments can be designated or allocated differently; relief can remove a penalty and its related interest; and special deadlines can arise from disasters, combat-zone service, bankruptcy, or overseas filing rules. An audit or amended return also follows different payment and penalty starting points.

This calculator deliberately refuses to carry the latest interest rate into a quarter the IRS has not published. It also labels the missing failure-to-pay penalty interest instead of inventing an assessment date. Use the result to understand the moving parts and compare scenarios, then use the notice, account transcript, or official payoff amount for an actual payment decision.

Outside scope: Form 2210 estimated-tax additions, corporations, partnerships and S corporations, payroll/deposit penalties, fraud, accuracy-related penalties, substitute returns, audit deficiencies, collection fees, and relief eligibility. For a penalty-free underpayment or delayed refund calculation, use the separate IRS interest and refund calculator.

Official sources and calculation transparency

• IRS failure-to-file penalty — monthly rate, cap, overlap, and minimum table.
• IRS failure-to-pay penalty — standard, installment-agreement, post-levy, and partial-month rules.
• IRS interest guidance — separate penalty interest start dates.
• IRS quarterly interest rates — the history used by the daily engine.
• Internal Revenue Manual 20.1.2 — detailed penalty periods, coordination, and indexed minimums.

For a plain-language walkthrough, read IRS late-filing and late-payment penalties explained. The existing IRS interest-rate guide explains the quarterly benchmark and daily compounding.

Frequently asked questions

Related IRS tools

• IRS interest and delayed-refund calculator — interest-only scenarios for individuals and corporations.
• Current IRS underpayment rate and quarterly history — inspect every recorded rate period since 2017.
• IRS filing and payment penalties explained — a plain-language walkthrough of the rules and exclusions.