IRS Underpayment Penalty: Safe Harbors, Due Dates, and Waivers

The IRS underpayment penalty is an interest-style charge that applies when your withholding and estimated tax payments during the year fall short of what you owed. You trigger it if you still owe at least $1,000 at filing time and didn’t meet one of the safe harbors: paying in at least 90% of the current year’s tax, or 100% of last year’s tax (110% if your prior-year AGI topped $150,000, or $75,000 if married filing separately).¹² The rate is 7% annually for the first quarter of 2026 and 6% for the second quarter, compounded daily on each installment shortfall.³⁴

When the Penalty Applies

Two conditions must both be true. First, your balance due after subtracting withholding and refundable credits has to be $1,000 or more. Owe less than that and no penalty applies, no matter how the payments were timed.²

Second, your combined withholding and estimated payments didn’t meet either safe harbor described below. Hit one of them and you’re protected even if the final balance due is large.¹

There is also an exception that wipes out the penalty entirely. If you had zero tax liability for the prior year, the prior year covered a full 12 months, and you were a U.S. citizen or resident the whole year, no penalty applies at all.⁵

The Two Safe Harbors

90% of the Current Year

Pay in at least 90% of the tax shown on this year’s return, through any combination of withholding and estimated payments, and the penalty is off the table.⁶ The catch is that you have to hit the number before you actually know it. For someone on a steady salary that’s not hard. For freelancers, business owners, or anyone with investment gains, the target moves as the year goes on.

100% or 110% of Last Year

The prior-year safe harbor is the reliable one because the number is already fixed. Pay in at least 100% of last year’s total tax and you’re protected, regardless of how much you actually owe this year. If your prior-year AGI was over $150,000 (or over $75,000 for married filing separately), the threshold rises to 110%.² The prior year has to have been a full 12-month tax year with a filed return; otherwise this safe harbor isn’t available.

How the Penalty Is Calculated

The penalty isn’t a flat charge. It works like interest, accruing daily on the amount you were short for each installment period, from that installment’s due date until the shortfall is paid or the return is filed. The rate is the federal short-term rate plus three percentage points and resets each calendar quarter.⁷

For 2026, the underpayment rate is 7% for the first quarter and 6% for the second.³⁴ Later quarters may move again with the federal short-term rate.

A rough example. Say you were short by $2,000 on the April installment and paid nothing more until you filed a year later. At roughly 7% annually with daily compounding, that shortfall generates about $145 in penalty. In practice the rate shifts each quarter and any later payment reduces the balance, so the real figure depends on the specifics. The design approximates interest on late money, not a punitive fine.

The penalty is figured separately for each installment period. That’s the part people miss. Overpaying in December doesn’t erase interest that already accrued on an April shortfall, at least when you’re relying on estimated payments alone. Withholding follows a different rule, discussed below.

The Quarterly Due Dates

The tax year is divided into four unequal installment periods, each with its own deadline. For 2026:⁸

1st installment: April 15, 2026
2nd installment: June 15, 2026
3rd installment: September 15, 2026
4th installment: January 15, 2027

Each installment generally equals 25% of the required annual payment.

Using Withholding to Fix a Shortfall

Federal income tax withheld from paychecks, pensions, or other payments is treated as paid in four equal installments across the quarterly due dates, no matter when in the year the withholding actually happened.² Estimated payments, by contrast, count only toward the quarter in which you actually make them.

That difference matters if you realize late in the year that you’ve fallen behind. Filing a revised W-4 to boost withholding on your remaining paychecks retroactively spreads that money across all four quarters for penalty purposes. A single estimated payment in October only helps the third and fourth quarters. Anyone who took a big bonus, sold appreciated stock, or had a late-year income surprise can often eliminate earlier-quarter penalties this way.

Uneven Income: The Annualized Method

If your income arrived unevenly, the standard equal-quarters calculation can overstate what you owed early in the year. The annualized income installment method recalculates each quarter’s required payment based on income actually earned through that point.⁹

The method uses four cumulative income periods (January–March, January–May, January–August, and the full year). For each period, you annualize the income to a full year, figure the tax, and derive the required installment. When most of the income arrived in the fall, this shifts the obligation to later quarters and often shrinks the penalty considerably.

Using the method requires Schedule AI on Form 2210, attached to your return. If you use it for one period, you have to use it for all four, and you need records of when income was received and deductions were paid.

When the IRS Can Waive the Penalty

Even when the penalty technically applies, the IRS can waive it in two situations.

The first is a casualty, disaster, or other unusual circumstance where imposing the penalty would be against equity and good conscience. Federally declared disaster areas are the most common trigger.¹⁰ The standard is broad, which gives the IRS room to grant relief but also means there’s no formula.

The second applies if you retired after reaching age 62, or became disabled, in either the tax year the payments were due or the year before, and the underpayment was due to reasonable cause rather than willful neglect.¹¹ Either waiver is requested by checking box A in Part II of Form 2210 and filing page 1 with your return.

How the Penalty Gets Reported

In most cases you don’t calculate the penalty yourself. File Form 1040 without Form 2210 attached, and the IRS figures the amount, either adding it to your balance due or subtracting it from your refund.¹²

You do need to file Form 2210 yourself when using the annualized income installment method, requesting a waiver, or documenting that withholding actually occurred on specific dates rather than evenly. Skip the form in those situations and the IRS will use its standard calculation, which may produce a higher number than you’d owe under the special method.

Farmers, Fishermen, and State Rules

If at least two-thirds of your gross income comes from farming or fishing in either the current or prior year, different rules apply. You can make a single estimated payment by January 15, or skip estimated payments entirely by filing your return and paying the full balance by March 1 of the following year.¹³ If March 1 falls on a weekend or holiday, the deadline moves to the next business day.

State underpayment penalties are separate. Most states with an income tax impose their own, and the rates, safe harbor percentages, and minimum-balance triggers don’t always match the federal ones. Meeting the federal safe harbors doesn’t guarantee you’re clear at the state level, so check your state tax authority’s rules directly.

1
Internal Revenue Service. Topic No. 306, Penalty for Underpayment of Estimated Tax
2
Office of the Law Revision Counsel. 26 USC 6654 Failure by Individual To Pay Estimated Income Tax
3
Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
4
Internal Revenue Service. Internal Revenue Bulletin 2026-8
5
Internal Revenue Service. Penalty Questions
6
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
7
Internal Revenue Service. Quarterly Interest Rates
8
Internal Revenue Service. 2026 Form 1040-ES, Estimated Tax for Individuals
9
Internal Revenue Service. Instructions for Form 2210 (2025)
10
Internal Revenue Service. Penalty Relief Due to Statutory Exception
11
Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty – Section: Remove or Reduce a Penalty
12
Internal Revenue Service. Form 2210, Underpayment of Estimated Tax by Individuals, Estates, and Trusts
13
Internal Revenue Service. Topic No. 416, Farming and Fishing Income