Quarterly tax set-aside estimator (2026)

What this estimates

Self-employment tax is 15.3% (12.4% Social Security + 2.9% Medicare) on 92.35% of your net profit. For 2026 the Social Security part applies to the first $184,500. Above $200,000 (single) or $250,000 (married filing jointly), a 0.9% Additional Medicare Tax applies. If 92.35% of your profit is under $400, no SE tax is due.

Income tax: half of the SE tax is deducted to get adjusted gross income, then the 2026 standard deduction ($16,100 single, $32,200 married filing jointly), then the 2026 brackets (10%, 12%, 22%, 24%, 32%, 35%, 37%).

Worked example, single, $80,000 profit: SE tax $11,303.64; taxable income $58,248.18; federal income tax $7,526.60; total $18,830.24, or $4,707.56 a quarter (about 23.5% of profit).

When you have to pay

The IRS splits the year into four periods with due dates of April 15, June 15, September 15 and January 15 of the following year. Its estimated-tax page says you can generally avoid the underpayment penalty if you owe less than $1,000 after withholding and credits, or if you paid at least 90% of this year's tax or 100% of last year's. If your 2025 adjusted gross income was over $150,000 ($75,000 if married filing separately), the prior-year figure is 110% instead of 100% (IRS Publication 505).

What it leaves out

The qualified business income (QBI) deduction, retirement contributions, health insurance deductions, credits, itemized deductions, head-of-household status and W-2 wages counting toward the Social Security cap. Most of these lower your tax, so treat the result as a cautious upper estimate.

FAQ

Sources

• IRS — Self-employment tax (Social Security and Medicare taxes) — 15.3% rate, 2026 $184,500 Social Security cap, Additional Medicare thresholds
• IRS — Topic no. 554, Self-employment tax — 92.35% of net earnings, $400 threshold, deduct one-half of SE tax
• IRS — Schedule SE (Form 1040) — line 4a ×92.35%, line 10 ×12.4%, line 11 ×2.9%, line 13 ×50%
• SSA — Contribution and benefit base — $184,500 for 2026
• IRS — Tax inflation adjustments for tax year 2026 — 2026 standard deduction and bracket thresholds
• IRS — Estimated taxes — due dates April 15, June 15, Sept. 15, Jan. 15
• IRS — Estimated taxes (businesses) — $1,000 threshold; 90% current year / 100% prior year safe harbors
• IRS — Publication 505 (2026), Tax Withholding and Estimated Tax — 110% prior-year safe harbor if 2025 AGI over $150,000 ($75,000 MFS)

Figures last checked: November 2, 2026. The QBI deduction is not included. Not legal or tax advice.