Beaconshire Advisory · www.beaconshireadvisory.com · Quarterly Estimated Tax & Self-Employment Tax Calculator (2026) · printed
Calculator · Tax
What do I actually owe — and what should each quarterly payment be?
Project your 2026 self-employment tax, federal income tax (with the §199A deduction and the 2026 brackets), and state tax — then compute the safe-harbor payment that keeps the IRS penalty off your return. Enter what you know; the calculator fills in the rules.
Where the money goes
Your projected 2026 tax by component.
Payment schedule
Federal estimated installments for tax year 2026. Installments split the remaining safe-harbor amount evenly; state estimates follow a similar calendar in most states.
The computation, line by line
Follows the order of Form 1040 and Schedule SE.
What this means
Reading the numbers the way a planner would.
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How it works
Methodology & assumptions
- Self-employment tax. Net profit × 92.35% is the SE base. Social Security applies at 12.4% up to the 2026 wage base of
$184,500less any W-2 wages you already earned; Medicare applies at 2.9% with no cap; an extra 0.9% applies above $200,000 ($250,000 MFJ, $125,000 MFS). One-half of the SE tax (excluding the 0.9%) is deducted in arriving at AGI, exactly as on Schedule 1. - Federal income tax. Taxable income = AGI − the larger of the 2026 standard deduction (
$16,100single /$32,200MFJ /$24,150HOH) or your itemized total, − the §199A deduction. Ordinary income runs through the seven 2026 brackets; qualified dividends and long-term gains are stacked on top at 0 / 15 / 20%. - §199A (QBI) deduction. 20% of qualified business income (net profit less the half-SE deduction, SE health insurance and owner retirement contributions), capped at 20% of taxable income before the deduction. Above
$201,750single /$403,500MFJ the deduction phases out for specified service businesses over a$75,000 / $150,000range, and is limited to 50% of W-2 wages paid for other businesses. The new $400 minimum deduction is applied where it exceeds the computed amount. The 2.5%-of-UBIA alternative limit is not modeled. - Credits. Child tax credit of
$2,200per child under 17, phased out at $50 per $1,000 of AGI above $200,000 ($400,000 MFJ). Enter any other credits directly. Refundability is not modeled. - Surtaxes. Net investment income tax at 3.8% on the lesser of investment income or AGI above $200,000 / $250,000 / $125,000. Additional Medicare tax on wages and SE income above the same thresholds.
- Senior deduction. If you check 65+, the calculator adds the extra standard deduction ($2,050 unmarried / $1,650 married, per person) and the OBBBA $6,000 senior deduction, reduced by 6% of MAGI above $75,000 ($150,000 MFJ).
- State tax. Approximated as your state’s flat or top marginal rate × federal AGI. States differ in starting point, deductions and credits; this is a planning placeholder, not a state return.
- Safe harbor. The required annual prepayment is the smaller of 90% of projected 2026 tax or 100% of 2025 tax (110% if 2025 AGI exceeded $150,000 / $75,000 MFS). Withholding counts first; the remainder is divided evenly across the installments you have left. No estimates are needed if you would owe under $1,000 at filing.
- Not modeled. Alternative minimum tax, the new tips/overtime/car-loan-interest deductions, education credits, earned-income credit, Kiddie tax, foreign income, state-specific credits, and the annualized-income installment method.
This calculator is an educational estimate built from published figures and the assumptions listed above. It is not tax, legal, or financial advice, does not account for every provision that may apply to you, and is not a substitute for a return prepared from your actual records. Figures are checked when published and may lag mid-year changes.
Questions
Common questions
Who has to make estimated payments?
Generally anyone who expects to owe at least $1,000 in federal tax for 2026 after withholding and refundable credits — which describes nearly every profitable sole proprietor, partner, S-Corp owner with distributions, landlord, and investor without enough withholding. The alternative is to increase W-2 withholding (yours or a spouse’s), which the IRS treats as paid evenly through the year regardless of when it was withheld.
What happens if I only pay the safe-harbor amount?
You avoid the underpayment penalty, but you still owe the difference when you file on April 15, 2027. The safe harbor protects your timing, not your total. If this year’s projection is much higher than last year’s tax, set the difference aside now.
I missed earlier quarters. Can I catch up in January?
You can pay, and you should — but the penalty is computed installment by installment, so a January catch-up stops the clock on future quarters without erasing the earlier shortfall. If your income arrived unevenly during the year (a Q4 bonus, a seasonal business), Form 2210 Schedule AI lets you annualize and may remove most of the penalty. The rate is 7% per year (Q4 2026), so the penalty on a few thousand dollars for a few months is small; just don’t ignore it.
Why does my S-Corp income not show self-employment tax?
Because it is not subject to it. S-Corp owners pay FICA through payroll on their salary; distributions avoid both SE and FICA tax. Enter your S-Corp salary as W-2 wages and distributions as other ordinary income. To see what the election is worth, use the S-Corp vs. LLC calculator.
How accurate is the state estimate?
It is a placeholder. Flat-tax states (Indiana at 2.95%, Illinois, Pennsylvania, and a dozen others) come out close. Graduated states like California or New York will be overstated at moderate incomes because the calculator applies the top rate; enter your effective rate for a better figure. County and city taxes (Indiana counties, NYC, Philadelphia) are not included.
Does this handle the 2025 tax law changes?
Yes, where they affect 2026: the permanent 20% QBI deduction with wider phase-in ranges and the $400 minimum, the $40,400 SALT cap, the $6,000 senior deduction, the $2,200 child tax credit, and the 2026 inflation-adjusted brackets and standard deduction from Rev. Proc. 2025-32. The new deductions for tips, overtime and car-loan interest are not modeled.
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