IRS Penalties and Interest Calculator

Calculation scope

Calculation mode

Taxpayer type

Tax form

Tax year

Filing status

Partners or shareholders

Used for Forms 1065 and 1120-S.

Return type

Tax period

Taxpayer location

Dates and status

Original return due date

Extended filing due date

Actual filing date

Original payment due date

Calculate through date

IRS assessment date

IRS notice date

Notice payment deadline

Installment agreement start

Installment agreement end

Intent-to-levy notice date

One-percent levy rate start

Relief effective date

Accuracy penalty assessment date

Estimated penalty assessment date

Approved filing extension

Return filed on time

Farmer or fisher special rule

Tax, credits, and existing balance

Total tax shown on return

Tax required to be shown

Federal withholding

Timely estimated-tax payments

Extension payment

Refundable credits

Other timely payments

Prior-year credit applied

Additional IRS-assessed tax

Existing penalties

Existing interest

Payment allocation assumption

Partial payments

Payment date

Amount

Label

Payments on or before the payment due date reduce the opening unpaid tax.

Interest settings

Rate source

Interest category

Custom or fallback annual rate

Display rounding

Estimated-tax underpayment module

Calculate a Form 2210-style estimate

Current-year total tax

Prior-year total tax

Current-year withholding

Prior-year adjusted gross income

Installment method

Withholding timing

Estimated penalty waiver

Quarterly requirements and payments

Quarter	Annualized required amount	Payment amount
Q1	$	$
Q2	$	$
Q3	$	$
Q4	$	$

Actual withholding rows

Date

Amount

Accuracy-related penalty and relief

Include accuracy-related estimate

Affected underpayment

Penalty rate

Relief scenario

Penalty reduction

Accrue interest after other penalty assessments

Apply relief to failure-to-file

Apply relief to failure-to-pay

Apply relief to estimated-tax estimate

Apply relief to accuracy penalty

Treat relief as retroactive

Formula used

Failure-to-file estimate = unpaid tax × monthly filing rate × late months. Failure-to-pay estimate = unpaid tax balance × applicable monthly payment rate. Daily interest = prior balance × annual rate ÷ days in year. Next-day balance = prior balance + daily compounded interest. Estimated-tax penalty = daily underpayment × applicable quarterly rate.

The standard filing rate is generally five percent monthly. Overlapping payment penalties reduce that filing rate. The filing charge normally stops after five months.

The payment penalty generally uses one-half percent monthly. Approved individual plans may use one-quarter percent. Certain levy situations may use one percent.

IRS interest rates can change every calendar quarter. Interest generally compounds daily on unpaid balances. Missing future rates use the entered fallback rate.

How to use this calculator

Select the taxpayer, return, and calculation mode.
Enter filing, payment, notice, and assessment dates.
Enter tax, credits, withholding, and prior payments.
Add each later payment using its actual date.
Enable estimated-tax or accuracy modules when relevant.
Choose official rates or enter one custom rate.
Review relief assumptions before calculating the estimate.
Export the schedule for discussion and recordkeeping.

Example data

Input	Example value	Purpose
Tax required	$10,000	Starting federal tax liability.
Withholding	$5,000	Reduces unpaid tax.
Estimated payments	$1,000	Reduces unpaid tax.
Original due date	April 15	Starts payment charges.
Filing date	July 20	Determines filing months.
Calculation date	September 30	Ends the estimate.

Important limitations

This calculator provides educational planning estimates only. It cannot determine legal eligibility for penalty relief. An official IRS notice controls the amount owed.

Payment allocation and assessment dates can change results. Disaster postponements can also change statutory deadlines. Enter adjusted dates when official relief applies.

Partnership and S corporation rules depend on ownership counts. International forms can carry separate information-reporting penalties. Those specialized charges require separate review.

Official sources: failure-to-file penalty, failure-to-pay penalty, quarterly interest rates, and estimated-tax guidance.

Frequently asked questions

Does a filing extension delay payment?

No. An extension usually changes only the filing deadline. Tax generally remains due on the original payment date.

How are partial months counted?

Late-filing and late-payment penalties generally count partial months. Even one late day can create one monthly charge.

Can both penalties apply together?

Yes. The filing penalty is generally reduced during overlapping months. The payment penalty can continue after filing.

Does interest compound daily?

IRS underpayment interest generally compounds daily. The applicable annual rate can change quarterly.

Can an installment agreement reduce penalties?

An approved individual agreement may reduce the monthly payment penalty. Interest normally continues until full payment.

What happens after a levy notice?

The payment penalty can rise after specified notice requirements. Enter the effective one-percent rate date carefully.

Does first-time relief remove interest?

Relief may remove qualifying penalties. Related interest may then be recomputed. Other interest generally remains payable.

Why can the IRS amount differ?

The IRS uses transcript dates and statutory allocation rules. Notices can include assessments unavailable to this calculator.

How are partnerships calculated?

Late partnership returns can use monthly per-partner charges. S corporation returns can use similar per-shareholder charges.

Are future quarterly rates included?

Only published rates should be treated as official. The calculator flags missing quarters and uses your fallback rate.

Should this replace professional advice?

No. Complex notices, audits, abatements, and litigation need professional review. Always compare estimates with IRS records.