The IRS underpayment penalty is an interest charge the government adds when you haven’t paid enough federal income tax during the year through withholding or estimated payments. For the first quarter of 2026 the rate is 7% annually, dropping to 6% for the second quarter, compounded daily on whatever you were short for each installment period.1Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 20262Internal Revenue Service. Internal Revenue Bulletin 2026-8 You can avoid it entirely by hitting one of two safe harbors, even if you still owe a large balance at filing time.
When the Penalty Applies
Two things have to be true before the IRS charges a penalty. Your balance due after subtracting withholding and refundable credits has to be $1,000 or more, and your payments during the year have to fall below both safe harbor thresholds.3Office of the Law Revision Counsel. 26 USC 6654 Failure by Individual To Pay Estimated Income Tax Owe less than $1,000 after withholding, and the penalty doesn’t apply regardless of how uneven your payments were.
One additional exception removes the penalty completely. If your total tax for the prior year was zero, the prior year covered a full 12 months, and you were a U.S. citizen or resident the entire year, you don’t owe an underpayment penalty for the current year no matter what.4Internal Revenue Service. Penalty Questions
The Two Safe Harbors That Prevent It
Meeting either safe harbor through combined withholding and estimated payments protects you, even if your final tax bill turns out much higher than you planned for.5Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
90% of This Year’s Tax
Pay in at least 90% of the tax shown on your current-year return and no penalty applies.6Internal Revenue Service. Topic No. 306, Penalty for Underpayment of Estimated Tax The catch is obvious: you have to predict your current-year income closely enough to hit the number before you know what it will be. Fine for a steady salary, difficult for freelancers, investors, or anyone with variable income.
100% or 110% of Last Year’s Tax
The prior-year safe harbor is more useful for planning because the number is already fixed. Pay in at least 100% of last year’s total tax and you’re protected, whatever this year brings. If your prior-year adjusted gross income was over $150,000 ($75,000 if married filing separately), the threshold climbs to 110%.3Office of the Law Revision Counsel. 26 USC 6654 Failure by Individual To Pay Estimated Income Tax
Two conditions limit this safe harbor. The prior year must have been a full 12-month tax year, and you must actually have filed a return for it. Without a filed prior-year return, there is no prior-year safe harbor to lean on.
Quarterly Due Dates
The IRS splits the year into four installment periods, each with its own deadline. For 2026 the dates are:7Internal Revenue Service. 2026 Form 1040-ES, Estimated Tax for Individuals
- First installment: April 15, 2026
- Second installment: June 15, 2026
- Third installment: September 15, 2026
- Fourth installment: January 15, 2027
Each installment generally equals a quarter of your required annual payment, and the penalty is figured separately for every period. Being short on the first quarter creates a penalty for that quarter even if you overpay later. Catching up in December doesn’t erase interest that already accrued on earlier shortfalls when you’re relying on estimated payments alone.
How the Penalty Is Calculated
This isn’t a flat fee. The IRS applies the underpayment rate (the federal short-term rate plus three percentage points) to each quarter’s shortfall, running from that quarter’s due date until you pay or until the filing deadline, whichever comes first.8Internal Revenue Service. Quarterly Interest Rates The rate resets each calendar quarter.
A quick example. If you owed a $2,000 required installment on April 15 and paid nothing until filing the following April, one full year of daily compounding at 7% would produce roughly $145 in penalty. Actual results shift as the rate changes each quarter and as partial payments reduce the balance, but the design is clear: the charge approximates interest on money the Treasury should have had sooner, not a punitive fine.
Fixing a Late-Year Shortfall With Withholding
Federal income tax withheld from paychecks, pensions, or similar payments is treated as paid in four equal installments across all quarterly due dates, no matter when during the year the withholding actually happened.3Office of the Law Revision Counsel. 26 USC 6654 Failure by Individual To Pay Estimated Income Tax Estimated payments only count toward the quarter in which you make them.
That asymmetry is useful. If you realize in October that you’ve underpaid all year, filing a revised W-4 and loading extra withholding onto your remaining paychecks spreads that money back across all four quarters for penalty purposes. A single large estimated payment in October only helps the third and fourth quarters. For anyone hit by a late-year bonus, stock sale, or other surprise income, boosting withholding can wipe out penalties for earlier periods that would otherwise be locked in.
Annualized Income for Uneven Earnings
If your income arrived unevenly (a large commission in November, a December capital gain, seasonal business revenue), the standard quarter-by-quarter calculation can overstate what you should have paid early in the year. The annualized income installment method lets you recalculate each quarter’s required payment based on income actually received through that point.9Internal Revenue Service. Instructions for Form 2210 (2025)
The method uses four cumulative periods: January through March, January through May, January through August, and the full year. For each one, you figure tax as if that period’s income were projected to a full year, then determine the required installment. Early quarters with low income carry a smaller required payment, shifting more of the obligation to later periods when income actually arrived.
You complete Schedule AI on Form 2210 to use this method and must apply it to all four installment periods if you apply it to any. Tax software handles the arithmetic, but you need records of when income was received and when deductible expenses were paid.
Waivers for Disaster, Retirement, or Disability
Two statutory waivers can erase the penalty even when you technically owe it. The first covers casualty, disaster, or other unusual circumstances where imposing the penalty would be against equity and good conscience. Federally declared disaster areas are the common trigger.10Internal Revenue Service. Penalty Relief Due to Statutory Exception The standard is broad, which gives the IRS discretion but means there’s no automatic formula.
The second applies if you retired after reaching age 62 or became disabled, either in the year the payments were due or the year before, and the underpayment was due to reasonable cause rather than willful neglect.11Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty – Section: Remove or Reduce a Penalty You request either waiver by checking box A in Part II of Form 2210 and filing page 1 with your return.
A Different Rule for Farmers and Fishermen
If at least two-thirds of your gross income (current year or prior year) comes from farming or fishing, the rules are simpler. You can make a single estimated payment by January 15 and avoid the penalty, or skip estimated payments entirely by filing your return and paying the full balance by March 1 of the following year. If March 1 falls on a weekend or holiday, the deadline moves to the next business day.12Internal Revenue Service. Topic No. 416, Farming and Fishing Income
How It Gets Reported and Paid
In most cases you don’t calculate the penalty yourself. File Form 1040 without attaching Form 2210 and the IRS will figure the penalty, then either add it to your balance due or subtract it from your refund.13Internal Revenue Service. Form 2210, Underpayment of Estimated Tax by Individuals, Estates, and Trusts
You do need to file Form 2210 yourself in three situations: when you’re using the annualized income method, when you’re requesting a waiver, or when you want to show that withholding was concentrated in specific periods rather than spread evenly. Skip the form in those cases and the IRS will use the standard calculation, which may produce a higher number than you actually owe. The penalty itself is paid like any other tax balance: electronically through IRS Direct Pay, by check, or subtracted from your refund.
State Penalties Are Separate
Most states that tax income have their own underpayment penalties, and the rules don’t always track the federal ones. State rates, safe harbor percentages, and minimum balance triggers vary. Meeting the federal safe harbors does not automatically protect you from a state penalty, so check your state tax authority’s rules separately.