2026 tax year · US · Updated June 11, 2026

Estimated Tax Penalty Calculator

Missed a quarterly payment, or paid less than the safe harbor required? This calculator turns that shortfall into the exact dollar figure the IRS will charge, using the same day-count math as Form 2210.

Your missed payment

$
How much less than the required payment you paid for that quarter

Your penalty

Estimated penaltySection 6654 underpayment penalty on this shortfall
$30.25
Days lateFrom the day after the deadline through the payment date
92 days

By rate period

PeriodDaysRateAmount
Jun 15, 2026 to Jun 30, 2026156%$4.93
Jun 30, 2026 to Sep 15, 2026776%*$25.32

* Days after June 30, 2026 use the latest announced rate (6%); the IRS announces each quarter’s rate shortly before it begins.

This penalty is simple interest: it never compounds daily, because IRC section 6622(b) excludes it from the daily compounding the IRS applies to other balances. Paying sooner stops the clock on the day you pay. The calculator covers the tax year 2026 quarterly deadlines, with accrual capped at Apr 15, 2027.

How the penalty is calculated

Despite the name, this penalty is interest, not a fine. There is no flat charge for missing a deadline; the IRS simply charges the federal underpayment rate on your shortfall for every day it stays unpaid. The math is shortfall, times the annual rate, times days late, divided by 365. And unlike the interest the IRS charges on an unpaid bill after you file, this one never compounds: IRC section 6622(b) specifically excludes the section 6654 penalty from daily compounding, so the charge grows in a straight line.

That makes the stakes concrete. Underpay the June installment by $4,000 and catch up 60 days later, and the penalty at the 6% rate in effect since April 1, 2026 is about $39. Real money, but rarely the catastrophe people fear, and every day sooner you pay shaves a little off.

The cheaper move is never owing it at all. The penalty only applies when you miss the safe harbor: paying in at least 90% of this year’s tax or 100% of last year’s (110% above $150,000 AGI), through withholding or estimates. Our quarterly tax calculator computes that target, and if you also have a W-2 job, the W-4 withholding calculator shows how extra withholding can cure a shortfall even late in the year. For waivers, the annualized income method, and how stacked shortfalls interact, see the full estimated tax penalty guide.

These are estimates, not tax advice. The calculator models a single shortfall against tax year 2026 deadlines; multiple underpaid quarters each accrue separately on Form 2210.

Where these numbers come from

The penalty is computed with the Form 2210 day-count method: underpayment, times the quarterly federal underpayment rate, times days late, divided by 365, as simple interest. Every rate is transcribed from these sources:

Constants last verified against these sources on June 11, 2026. Every value is also pinned by an automated test suite that fails if a rate in the calculator drifts from the figure we transcribed from the source.

Frequently asked questions

How is the estimated tax penalty computed?
It is day-count interest on your shortfall: the amount you underpaid, times the federal underpayment rate, times the number of days late, divided by 365. Form 2210 runs that math separately for each rate period the lateness spans. It is simple interest, so the charge grows in a straight line, not exponentially.
What are the underpayment rates for 2026?
7% for the first quarter of 2026 (January through March) and 6% for the quarter beginning April 1, 2026, per the IRS newsroom and Internal Revenue Bulletin 2026-22. The IRS sets the rate every calendar quarter at the federal short-term rate plus 3 percentage points, announcing each quarter's rate shortly before it begins.
Does the penalty compound daily like regular IRS interest?
No. IRC section 6622(b) specifically excludes the section 6654 estimated tax penalty from the daily compounding that applies to most IRS interest. Interest on an unpaid tax bill after filing compounds daily; this penalty does not, which is why it stays smaller than people expect.
When does the penalty stop accruing?
On the day you pay the shortfall, or at the return's filing deadline (April 15, 2027 for tax year 2026), whichever comes first. Each day you wait adds to the bill, so paying a missed installment as soon as you notice is always cheaper than waiting until you file.
How do I avoid the penalty entirely?
Hit a safe harbor: pay in, through withholding plus estimated payments, at least 90% of this year's tax or 100% of last year's total tax (110% if last year's adjusted gross income topped $150,000). There is also no penalty if you owe under $1,000 after withholding. Our quarterly estimated tax calculator computes the exact safe-harbor payment for your numbers.
Can the penalty be waived?
Sometimes. The IRS can waive it for casualty, disaster, or other unusual circumstances where charging it would be inequitable, and for taxpayers who retired after reaching age 62 or became disabled, if the underpayment was due to reasonable cause rather than willful neglect. Separately, if your income arrived unevenly (a big Q4 sale, seasonal work), the annualized income method on Form 2210 Schedule AI can shrink or eliminate the penalty by matching each installment to when you actually earned.
Is this calculator exact?
For a single shortfall it matches Form 2210's method: days late times the quarterly rate, divided by 365, applied per rate period. If you underpaid multiple quarters, each shortfall stacks and accrues on its own timeline, and the form computes them line by line; run each missed quarter through the calculator separately and add the results for a close estimate.

Other free calculators