The U.S. tax system is pay-as-you-go: most people prepay through paycheck withholding, but if you earn income that no employer withholds from, you generally have to send the government quarterly estimated tax payments. For 2026, the four due dates, the safe-harbor math, and the underpayment penalty all follow the same structure as recent years — with the calendar quirks that catch first-time filers. This guide explains who must pay, when, and how to avoid a penalty. The figures and procedures come from IRS Publication 505 and the IRS Taxpayer Advocate's 2026 tax-date list.
Who must pay estimated tax
You generally must make quarterly estimated payments if you expect to owe at least $1,000 in federal tax after subtracting withholding and refundable credits. The rule mainly catches people with income that arrives without withholding:
- Self-employment and independent-contractor (1099) income
- Interest, dividends, and capital gains not covered by withholding
- Rentals and royalties
- Taxable Social Security or pension income with little or no withholding
- A large one-time gain or bonus
Sole proprietors, partners, and S-corporation shareholders are subject to the same $1,000 threshold. C corporations use a lower $500 threshold. If your withholding and credits already cover the smaller of 90% of the current year's tax or 100% of last year's tax, you usually do not need to pay estimated tax separately.
The 2026 due dates
Estimated tax is paid in four installments, but the periods are not equal calendar quarters:
| Payment | Covers | Due date |
|---|---|---|
| 1st quarter | Jan 1 – Mar 31, 2026 | April 15, 2026 |
| 2nd quarter | Apr 1 – May 31, 2026 | June 15, 2026 |
| 3rd quarter | Jun 1 – Aug 31, 2026 | September 15, 2026 |
| 4th quarter | Sep 1 – Dec 31, 2026 | January 15, 2027 |
If a due date falls on a weekend or federal holiday, it moves to the next business day. You can skip the January 15 payment if you file your full return and pay any balance by January 31, 2027. Use Form 1040-ES to figure and pay; each voucher shows the period it covers.
Two ways to figure the amount
Method 1 — prior-year safe harbor (simplest). Take last year's total tax and divide by four. Pay that amount each quarter and you are protected from the underpayment penalty even if your income rises, because you met a safe harbor.
- If your prior-year AGI was $150,000 or less ($75,000 if married filing separately), the safe harbor is 100% of last year's tax.
- If your prior-year AGI was more than $150,000 ($75,000 if MFS), the safe harbor is 110% of last year's tax.
Method 2 — current-year estimate. Estimate your 2026 tax, subtract withholding, and pay the remainder in quarterly installments. This is better if income dropped, but it carries underpayment risk if your estimate is low. The annualized-income method (Form 2210) lets people with uneven income base each payment on what they actually earned that period.
The safe-harbor rule that prevents penalties
You avoid the underpayment penalty if your total payments during the year meet the smaller of:
- 90% of your actual 2026 tax, or
- 100% of your 2025 tax (110% if your 2025 AGI exceeded $150,000 / $75,000 MFS).
Meeting either test protects you even if you end up owing more at filing time. The penalty is calculated like interest — the IRS sets the rate each quarter using the federal short-term rate plus 3 percentage points, and it accrues for each day the payment is short.
How to pay
You can pay online through IRS Direct Pay (free, no registration) or the Electronic Federal Tax Payment System (EFTPS), by check with a Form 1040-ES voucher, or through IRS2Go. EFTPS is useful if you make multiple payments a year. Keep confirmation numbers for every payment.
State estimated tax
Most states with an income tax mirror the federal schedule, but thresholds and due dates vary, and a few states have no personal income tax at all. Always check the specific state's rules before relying on the federal dates.
Common mistakes
- Forgetting the fourth payment. The January 15 deadline is easy to miss after the holidays; missing it costs more in penalty than missing the first quarter.
- Underpaying after a windfall. A large capital gain or bonus in one quarter can push you past the safe harbor for the year — consider an extra payment tied to that income.
- Ignoring state obligations. Federal and state estimated payments are separate.
Model your full 2026 picture with the federal income tax estimator, or model self-employment layers with the self-employment & QBI calculator.
Disclaimer: This article is general educational information, not tax, legal, or investment advice. Dollar amounts come from the 2026 sources listed at the end of this article and may change. Before you act, talk to a licensed CPA, EA, or tax attorney about your own situation.