Third Quarter Taxes: Deadline, Safe Harbors, and Penalties

The third quarter estimated tax deadline for 2026 is Tuesday, September 15. Because the date falls on a weekday, no weekend or holiday extension applies. The payment covers income you earned from June 1 through August 31 that wasn’t subject to withholding, and it’s the third of four installments the IRS expects from taxpayers who will owe at least $1,000 beyond what’s already withheld from paychecks or pensions.¹

Who Owes a Third Quarter Payment

The federal system runs on pay-as-you-go. If you earn money without automatic withholding, the IRS expects installments through the year rather than a single payment at filing.² That sweeps in freelancers, independent contractors, landlords, investors with meaningful capital gains or dividends, and anyone with self-employment income. It also reaches W-2 employees whose side income or investment gains push the total bill past the threshold.

The trigger is simple: if you expect to owe $1,000 or more in federal income tax for 2026 after subtracting withholding and refundable credits, you generally need to make estimated payments.² Sole proprietors, partners, and S corporation shareholders are the groups the IRS singles out.

You can skip estimated payments only in one narrow case: you had zero tax liability for the prior year, that year covered a full 12 months, and you were a U.S. citizen or resident the entire time.³

Safe Harbors That Prevent a Penalty

The IRS won’t penalize you for underpayment if your total withholding and estimated payments meet either benchmark, whichever is smaller:

90% of your 2026 tax.
100% of the total tax on your 2025 return, provided that return covered a full 12 months.

The prior-year figure is already known, which makes it the easier target. But if your income drops in 2026, basing payments on last year’s higher tax can mean overpaying all year and waiting for a refund.⁴

Higher earners face a steeper bar. If your adjusted gross income on your 2025 return exceeded $150,000 (or $75,000 for married filing separately in 2026), the prior-year safe harbor rises to 110% instead of 100%.³ So if your 2025 tax was $20,000 and your AGI cleared $150,000, you’d need at least $22,000 paid in across the four installments to be safe under the prior-year method.

Figuring the Amount Due September 15

The simplest method is to take your required annual payment, divide by four, and send that amount each quarter. This works when income arrives at a steady pace.

If your income is lumpy or seasonal, equal quarters can force early overpayment. The Annualized Income Installment Method lets you base each payment on income actually earned through the end of that period. For the third quarter, you calculate the tax on income from January 1 through August 31, then subtract what you already paid in Q1 and Q2. The remainder is your Q3 payment.⁵ It takes more recordkeeping, but the savings can be real when income spikes or dips mid-year.

Credit From a Prior-Year Refund

If you overpaid on your 2025 return and elected to apply the refund to 2026 estimated tax, the IRS credits that amount to your first installment; any excess carries forward. When you file for 2026, you’ll report estimated payments on Form 1040, line 26, including the carryover.⁶

Adjusting After an Income or Status Change

If income drops, a large contract lands, or your filing status changes because of marriage or divorce, rework your estimate using a fresh Form 1040-ES worksheet and adjust future payments.² If you overpaid earlier in the year, you can reduce the Q3 or Q4 payment.

Name changes add a wrinkle. If you made payments under a former name after a marriage or divorce, attach a statement to the front of your 2026 paper return listing all payments made under the former name and Social Security number. If you filed jointly for 2025 but will file separately for 2026 (or vice versa), the prior-year safe harbor math gets more involved because you must allocate the prior joint liability between spouses.⁷

How to Pay by September 15

Several methods work, and the mix is shifting in 2026. Whichever you pick, the payment must be submitted or postmarked by September 15.

IRS Direct Pay

The most straightforward option for individuals. You pay directly from a checking or savings account through the IRS website or the IRS2Go app, with no fees and no pre-registration. Confirmation is immediate.⁸ Select “Estimated Tax” as the payment type and apply it to the correct tax year.

EFTPS

The Electronic Federal Tax Payment System has long been popular for business owners and high-volume filers because payments can be scheduled in advance. The IRS stopped accepting new individual enrollments through EFTPS in October 2025, and all individual taxpayers are expected to transition to Direct Pay or IRS Online Account by late 2026.⁹ If you’re already enrolled as an individual, you can keep using it for now but should plan to switch. Business taxpayers are unaffected.

Credit or Debit Card

You can pay by credit card, debit card, or digital wallet through IRS-approved third-party processors. Credit card payments carry a fee of roughly 1.75% to 1.85% of the payment amount; personal debit card payments cost a flat fee of about $2.10 to $2.15. None of that fee goes to the IRS.¹⁰ On a $5,000 payment, a 1.75% credit card fee adds $87.50, which is worth knowing before you swipe for the points.

Mail With Form 1040-ES

You can still mail a check or money order with the Form 1040-ES payment voucher. Each quarter has its own voucher with the due date printed in the upper-right corner. Make the check payable to “United States Treasury” and write your Social Security number and “2026 Form 1040-ES” on it. The mailing address depends on your state of residence and is listed in the Form 1040-ES instructions.⁷ For mail, the postmark controls timeliness. Keep your confirmation numbers and canceled checks; the IRS suggests holding proof of payment for at least three years.¹¹

What Missing the Deadline Costs

Paying late or short of the required installment triggers the underpayment penalty, which functions as interest on the shortfall. The IRS calculates it separately for each quarter, running from the missed due date until the tax is paid or until the annual return due date, whichever comes first.⁴

The rate equals the federal short-term interest rate plus three percentage points and resets each calendar quarter. For Q1 2026 it was 7% per year, compounded daily.¹² It dropped to 6% starting April 1, 2026.¹³ The Q3 rate is announced separately and can shift again. On a $2,000 underpayment, a 6% annual rate is modest over a few months, but the total climbs quickly when multiple quarters are short.

The penalty is computed on Form 2210. The IRS will often figure it for you if you simply file your return without the form, but if you used the annualized income method or qualify for an exception, you’ll need to file Form 2210 yourself to claim the lower amount.⁵

Waivers and Exceptions

Even if you technically underpaid, no penalty applies if your total tax after withholding and refundable credits is less than $1,000.³ Meeting either safe harbor also provides complete protection.

Beyond those automatic safe harbors, the IRS can waive the penalty in two situations. First, if the underpayment resulted from a casualty, disaster, or unusual circumstance and imposing the penalty would be inequitable, the IRS has discretion to waive it. Second, if you retired after reaching age 62 or became disabled during the year the payments were due (or the year before), and the underpayment was due to reasonable cause rather than neglect, the IRS can waive it entirely.³ Neither waiver is automatic. File Form 2210 and check the appropriate box to request relief.

Farmers and Fishermen Don’t Owe on September 15

If at least two-thirds of your gross income comes from farming or fishing, the four-installment schedule doesn’t apply. You can make a single estimated payment by January 15 of the following year, or skip estimated payments entirely if you file your return and pay the full balance by March 1.¹⁴ Either way, September 15 isn’t a deadline for you.

Fiscal year filers who qualify as farmers or fishermen follow their own schedule: pay all estimated tax by the 15th day after the end of the tax year, or file and pay in full by the first day of the third month after the tax year ends.¹⁴

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Internal Revenue Service. Individuals 2
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Internal Revenue Service. Estimated Taxes
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Office of the Law Revision Counsel. 26 U.S. Code 6654 – Failure by Individual to Pay Estimated Income Tax
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Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
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Internal Revenue Service. 2025 Instructions for Form 2210 – Underpayment of Estimated Tax by Individuals, Estates, and Trusts
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Internal Revenue Service. Estimated Tax
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Internal Revenue Service. Form 1040-ES – Estimated Tax for Individuals
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Internal Revenue Service. Direct Pay with Bank Account
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EFTPS. Welcome to EFTPS Online
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Internal Revenue Service. Pay Your Taxes by Debit or Credit Card or Digital Wallet
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Internal Revenue Service. Managing Your Tax Records After You Have Filed
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Internal Revenue Service. Interest Rates Remain the Same for the First Quarter of 2026
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Internal Revenue Service. Internal Revenue Bulletin: 2026-08
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Internal Revenue Service. Farmers and Fishermen