Quarterly Estimated Tax Calculator (2026)

Self-employment tax, income tax, and the safe harbor that avoids a penalty

Data verified: Aug 2026 · Source: IRS Rev. Proc. 2025-32

A quarterly estimated tax calculator for 2026: what to send the IRS each quarter, and the safe harbor that makes an underpayment penalty impossible.

Your details

Net self-employment income

$0 $400k

Business revenue less business expenses, before any self-employment tax. W-2 wages (if any)

Wages already subject to Social Security tax reduce the base your SE tax is charged on. Federal tax already withheld

From a job or a spouse's job. Withholding counts as paid evenly across all four quarters. Other taxable income

Interest, dividends, rental income and so on. Filing status Last year's total tax

Line 24 of your 2025 Form 1040. Leave at zero if this is your first year. Last year's AGI

Above $150,000 the safe harbor rises from 100% to 110% of prior-year tax. Claim the 20% qualified business income deduction

Pay each quarter

—

Total tax vs. business income

Net SE income

How this is calculated

If you have income that is not subject to withholding, the IRS expects you to pay tax on it four times a year rather than in one lump at filing. Miss those payments and you owe an underpayment penalty, charged as interest at a rate that resets quarterly — 7% in the first quarter of 2026, 6% in the second, and 7% again in the third.

The calculation stacks two separate taxes. Self-employment tax is 15.3% on 92.35% of your net business income, covering both halves of Social Security and Medicare. Federal income tax is then charged on your AGI after the deductible half of that SE tax, your standard or itemized deduction, and any qualified business income deduction.

Formula

netSE      = businessNet × 0.9235
ssTax      = min(netSE, $184,500 − w2SSWages) × 0.124
medicare   = netSE × 0.029
addlMed    = max(0, total wages − threshold) × 0.009
seTax      = ssTax + medicare + addlMed
halfSEded  = (ssTax + medicare) / 2        // above the line, excludes the 0.9%

incomeTax  = brackets(AGI − standard deduction − QBI)
total      = seTax + incomeTax − withholding
quarterly  = total / 4

The safe harbor under IRC §6654 is the smaller of 90% of this year's tax or 100% of last year's — 110% if your prior-year AGI exceeded $150,000, or $75,000 if married filing separately.

Worked example

A sole trader with $80,000 of net self-employment income and no other job.

Net earnings from self-employment: $80,000 × 0.9235$73,880

Self-employment tax at 15.3%$11,304

Deductible half of SE tax (reduces AGI)$5,652

Self-employment tax for the year$11,304

The safe harbor is the useful number

Estimating this year's income accurately is hard, especially if your work is lumpy. The safe harbor sidesteps that entirely: pay 100% of last year's total tax — 110% if your prior-year AGI was over $150,000 — spread across the four quarters, and you cannot be penalized regardless of what you actually earn. You still owe the balance at filing, but with no penalty attached. In a year where your income jumps, this is almost always the right approach.

Uneven income and the annualized method

The default assumption is that your income arrives evenly, so each quarterly payment should be a quarter of the year's tax. If your income is genuinely seasonal — most of it landing in the fourth quarter, say — the annualized income installment method on Schedule AI lets you pay in proportion to when you actually earned it, using cumulative thresholds of 22.5%, 45%, 67.5% and 90%. It is more paperwork but it stops you having to fund payments before the money exists.

Withholding is treated as paid evenly

Tax withheld from a paycheque is credited as if it were paid in equal amounts across all four quarters, regardless of when it was actually withheld. That creates a useful escape hatch: if you find yourself underpaid late in the year, increasing withholding on a W-2 job in December can retroactively fix earlier quarters in a way that a December estimated payment cannot.

Frequently asked questions

When are the 2026 payments due?

15 April 2026, 15 June 2026, 15 September 2026, and 15 January 2027. The quarters are deliberately uneven despite the name: the second covers only two months and the fourth covers four. If a due date falls on a weekend or federal holiday it moves to the next business day, and payments are treated as made on the postmark or electronic submission date.

What is the penalty if I skip a payment?

Interest on the underpaid amount at the federal short-term rate plus three points, compounded daily and reset every quarter. For 2026 that is 7% in the first quarter, 6% in the second and 7% in the third. It is charged per quarter, so a missed April payment accrues from April even if you overpay later in the year.

Why is SE tax charged on 92.35% of my income?

The factor approximates the employer half of payroll tax that an employee would never pay income tax on. Multiplying net business income by 0.9235 removes that employer-equivalent portion before the 15.3% rate is applied, which keeps self-employed people roughly in line with employees. The deductible half of the resulting tax then comes off your AGI as well.

Do I still owe SE tax if I also have a job?

Yes, but the Social Security portion stops once your combined wages and self-employment earnings reach the $184,500 wage base for 2026, so W-2 wages effectively use up that allowance first. The 2.9% Medicare portion has no ceiling at all, and an extra 0.9% surtax applies above $200,000 single or $250,000 filing jointly.

Can I pay it all in one go?

You can pay early, but not late. Paying the whole year's tax in the fourth quarter does not cure missed earlier quarters, because the penalty is computed quarter by quarter. The one genuine exception is withholding from a W-2 job, which is treated as paid evenly across all four quarters no matter when it was actually withheld.

Does the QBI deduction reduce my SE tax?

No. The qualified business income deduction reduces taxable income for income tax purposes only. Self-employment tax is calculated on net business income before any QBI deduction is applied, so the 15.3% is unaffected. This catches people out, because the QBI deduction can look substantial while leaving the self-employment tax bill entirely unchanged.

Related calculators

Tips, Overtime, Car Loan & Senior Deductions Stack all four OBBBA deductions with their separate MAGI phaseouts. Severance Pay Tax Calculator What actually lands in your account after supplemental withholding. LLC Cost by State Filing fee, annual report, publication rules and five-year total for all 50 states. Roth Conversion Calculator Conversion room to the top of your bracket, with IRMAA and ACA warnings.

Sources

IRS Rev. Proc. 2025-32 · SSA Contribution & Benefit Base · Federal Reserve H.15 · IRS IR-2025-112 · IRS Rev. Rul. 2026-5 · IRS Rev. Rul. 2026-9

Disclaimer

Estimates for general information only, not tax advice. State and local estimated taxes, tax credits, the annualized income method, and the QBI wage/property limits and service-business exclusion above the phase-in threshold are not modeled here. Consult a qualified tax professional.