Quarterly Tax Calculator

What this quarterly tax calculator does

Most calculators divide your yearly tax by four. That is wrong if you have already paid something, started earning late, or want to avoid the penalty without paying more than you must. This one takes the payments you still have ahead and shows the amount for each, using the safe harbor rules: the smaller of 90% of this year’s tax or 100% of last year’s (110% for higher earners).

How to read the results

• Pay in each remaining installment is the amount that gets you to the safe harbor. It is the minimum that generally avoids the penalty.
• Per payment to cover it all is what you would pay to finish the year with nothing owed when you file.
• If you owe less than $1,000 after withholding and credits, no estimated payments are generally required.

Dates

For the 2026 tax year the dates are April 15, June 15 and September 15, 2026, and January 15, 2027. See all of them in the due dates guide.

Where the numbers come from

Your yearly tax is computed with the same engine as our self-employed tax calculator: self-employment tax, standard deduction, QBI and the 2026 brackets, plus the flat state rate you enter. Withholding from a W-2 job is not subtracted; enter your wages under tax settings, and add any withholding to “already paid” if you want it counted.

Frequently asked questions

How do I calculate quarterly taxes?

Estimate your net profit for the year, work out self-employment tax and income tax on it, then pay at least the safe-harbor amount spread over the remaining due dates. The calculator does the math.

What is the safe harbor for quarterly taxes?

Paying at least 90% of this year’s tax or 100% of last year’s (110% if last year’s AGI was above $150,000) generally avoids the underpayment penalty.

Can I pay everything in the last quarter?

You can, but a penalty may apply to the earlier quarters unless your income was uneven and you use the annualized method.

Is the January payment the fourth quarter?

Yes. The fourth payment for a tax year is due on January 15 of the next year, or the next business day.

Sources

• IRS: Estimated taxes
• IRS Publication 505: Tax withholding and estimated tax
• IRS Topic 306: Penalty for underpayment of estimated tax
• IRS: Self-employment tax (Social Security and Medicare)

Estimates only, not tax advice. See our disclaimer.

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