The estimated tax penalty is what the IRS charges when you don’t pay enough tax during the year, through withholding or quarterly estimated payments. For the self-employed it works like interest: a rate (7% a year for the fourth quarter of 2026, compounded daily) on the amount you were short, for the days it was late. It is usually smaller than people fear, and the safe harbor rules let you avoid it entirely.
Who owes it
Tax is pay-as-you-go. An employee’s tax is withheld from each paycheck; nobody withholds from a client’s payment, so the IRS expects you to pay four times a year. For the 2026 tax year the dates are April 15, June 15 and September 15, 2026, and January 15, 2027. You can owe the penalty if you’ll owe $1,000 or more when you file, after subtracting withholding and refundable credits, and you didn’t meet the safe harbor.
What it actually costs
Each quarterly payment is treated separately. The penalty on a payment is the amount you were short, times the IRS underpayment rate, for every day from its due date until you pay it or until the April filing date, whichever comes first. The rate is reset every quarter; it is 7% a year for October to December 2026.
A worked example: you were $2,000 short on the September 15, 2026 payment and paid it with your return on April 15, 2027. That’s 212 days. At 7% a year, compounded daily, the penalty is about $83. Unpleasant, not ruinous, and far less than borrowing the money elsewhere would cost. The real damage of skipping quarters is different: a large bill in April that you haven’t kept the cash for.
The safe harbor
You owe no penalty, however large your April bill, if your withholding and on-time estimated payments add up to at least the smaller of:
- 90% of your 2026 tax, or
- 100% of the tax on your 2025 return, or 110% if your 2025 adjusted gross income was over $150,000 ($75,000 married filing separately).
The prior-year test is the one to lean on when your income is hard to predict. You already know last year’s tax: divide it (or 110% of it) by four, pay that on each date, and any extra you owe this year is due in April with no penalty. If last year was your first year with no tax, and you were a US citizen or resident for the whole year, you owe no penalty this year at all.
If your income came late in the year
The penalty assumes you earned your income evenly. If most of it arrived in the autumn, that assumption overstates what you owed in April and June. The annualized income installment method (Schedule AI of Form 2210) works out each quarter’s required payment from what you had actually earned by then, which can cut the penalty for the early quarters to nothing. It’s more paperwork; tax software and accountants handle it, and it’s worth asking for if your year was back-loaded.
If you’ve already missed a payment
Pay it now. The penalty runs per day, so paying a missed September payment in November stops the clock two months in. You can pay through IRS Direct Pay or your IRS online account and choose the estimated tax option for 2026. And there’s one more option for the last quarter: if you file your 2026 return and pay everything you owe by February 1, 2027, you don’t need to make the January 15 payment at all.
Going forward, the steady fix is to set aside a share of every payment as it lands, so the quarterly dates are a transfer rather than a scramble. Our quarterly estimated tax calculator works out what each payment should be, and the quarterly guide covers how to pay.
Questions, answered
How much is the penalty for not paying estimated taxes?
It is calculated like interest: the IRS underpayment rate, 7% a year for the fourth quarter of 2026 and compounded daily, on the amount each quarterly payment was short, for the days it was late. Being $2,000 short on the September 15 payment until April 15 costs about $83.
How do I avoid the estimated tax penalty?
Owe less than $1,000 when you file, or pay at least the smaller of 90% of this year’s tax or 100% of last year’s (110% if your prior-year AGI was over $150,000) through on-time withholding and estimated payments.
Is there a penalty if I miss one quarterly payment?
Possibly, on that quarter only, and only for the days it is late. Paying it as soon as you can stops the penalty on that amount from growing.
Can the IRS waive the underpayment penalty?
It can, if the shortfall was caused by a casualty, disaster or other unusual circumstance, or if you retired after age 62 or became disabled in the year or the year before and had reasonable cause. You request it on Form 2210.
Sources
- Topic no. 306, Penalty for underpayment of estimated tax — IRS. The $1,000 threshold, the 90%/100% tests, the annualized method and waivers.
- Interest rates remain the same for the fourth quarter of 2026 — IRS. The 7% underpayment rate from October 1, 2026.
- Form 1040-ES, Estimated Tax for Individuals — IRS. The 2026 due dates, the 110% rule and the February filing exception.
- About Form 2210, Underpayment of Estimated Tax — IRS. How the penalty is figured, Schedule AI and waiver requests.
