The tax bill nobody sends you a reminder for

When you're self-employed, nobody withholds taxes from your checks. The IRS expects you to pay quarterly — four times a year, on a schedule that doesn't line up with calendar quarters. Miss these payments, or underpay by too much, and you'll owe penalties at filing even if you pay the full balance in April.

The 2026 due dates

Q1 (January 1 – March 31): due April 15. Q2 (April 1 – May 31): due June 16. Q3 (June 1 – August 31): due September 15. Q4 (September 1 – December 31): due January 15 of the following year. These are federal due dates — state deadlines vary, though most states follow the federal schedule.

Safe harbor — the penalty-free floor

You can avoid underpayment penalties entirely by paying at least as much as you owed last year. This is the safe harbor rule. If your prior year AGI was $150,000 or less, you need to pay 100% of last year's total tax liability. Above $150,000, the threshold increases to 110%. The calculator uses your prior year tax to determine which applies and flags when your projected tax exceeds the safe harbor amount.

Safe harbor is useful when income is variable — you pay based on what you know (last year's tax) rather than what you're guessing (this year's). If you had a particularly good year, you'll still owe the difference at filing, but you won't owe a penalty on top of it.

Self-employment tax and the deduction

SE tax is 15.3% on 92.35% of your net self-employment income (or 2.9% on amounts above the Social Security wage base, which is $176,100 in 2026, for the Medicare-only portion). You also get to deduct half of SE tax from your gross income before calculating federal and state income tax. The deduction reduces your taxable income but doesn't reduce SE tax itself.

How to pay

The IRS accepts estimated payments via EFTPS (Electronic Federal Tax Payment System), IRS Direct Pay, or mailing a check with Form 1040-ES. EFTPS is the most reliable for tracking and confirmation. Most states have their own estimated payment portals — search your state's department of revenue website for "estimated tax payments." Set a calendar reminder two weeks before each due date.

Results are estimates for planning purposes. This calculator uses simplified tax models and effective rates — actual tax may differ based on deductions, credits, and other income. Consult a CPA or enrolled agent for precise quarterly estimates.