IRS Penalty & Interest Calculator 2026-2030

Failure-to-File  •  Failure-to-Pay  •  Accuracy Penalty  •  Underpayment Interest  •  Tax Years 2023 - 2030
IRC §6651 (FTF/FTP) IRC §6698 / §6699 (Pass-through FTF) IRC §6601 / §6621 / §6622 (Interest) IRC §6662 (Accuracy)
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Return & Dates

Calendar-year taxpayers. The tax year sets the return due date and the inflation-adjusted minimum penalty amounts.
1065 and 1120-S use the per-partner / per-shareholder penalty of IRC §6698 / §6699, not IRC §6651.
An extension of time to file moves the failure-to-file start date. It does not extend time to pay. Treas. Reg. §1.6081-4(c), §1.6081-3(b).
Filled in from the tax year and return type (IRC §6072, shifted for weekends and D.C. legal holidays under IRC §7503). You may overwrite it.
Six months after the original due date, then shifted under IRC §7503. Used only if an extension was filed.
Defaults to today when the due date has passed, or to 90 days after the due date for a future year (illustrative).
Total tax on the return before withholding and payments (Form 1040 line 24 for 2025; total tax on Form 1120).
Payments and refundable credits made on or before the original due date. IRC §6651(b)(1). Amounts paid later belong in the payment date below.
Leave blank to assume the balance is paid on the filing date.
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Audit Adjustment & Accuracy Penalty (optional)

Deficiency attributable to the penalty basis you select. Leave at 0 if none.
IRC §6662(a), (b), (h), (i). The calculator applies the dollar test only for substantial understatement.
Leave blank to use the balance payment date above.
IRC §6662(d)(1)(C) substitutes 5 percent for 10 percent in the substantial understatement test.
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Interest Rate & Presumption Settings

FTF Penalty Rate
5%
Per month, max 25% - IRC §6651(a)(1)
FTP Penalty Rate
0.5%
Per month, max 25% - IRC §6651(a)(2)
Underpayment Interest
7%
Q4 2026, short-term rate + 3 - IRC §6621(a)(2), Rev. Rul. 2026-15
Accuracy Penalty
20% / 40%
Of underpayment - IRC §6662(a), (h), (i)
The IRS publishes each quarter's rate only about a month before the quarter starts (IRC §6621). Days after December 31, 2026 use this assumption and are labeled projected. Default is the latest published rate.
Treas. Reg. §301.6651-1(c)(3) (individuals) and (c)(4) (corporations): no failure-to-pay penalty for the extension period if at least 90% of the tax was paid by the original due date and the balance is paid with the return.
Quarterly rates for 2018 through Q4 2026 are the IRS-published underpayment rates. Interest is compounded daily (IRC §6622). Verify the current quarter at IRS.gov quarterly interest rates.
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Penalty & Interest Analysis

Enter your information above to calculate.
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Assumptions & Sources

Figures for periods after the IRS-published data (interest after December 31, 2026 and minimum penalty amounts for returns filed after 2027) are projected estimates, not IRS-published figures. Last verified: October 29, 2026.
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