Assumptions
- SE tax = 92.35% × net profit × (12.4% on the first $184,500 less W-2 wages + 2.9%) + 0.9% over $200,000. Half of SE tax deducted for AGI.
- Income tax = 2026 brackets on AGI − standard deduction − 20% QBI (simplified, no wage limit). Other income taxed as ordinary; no credits.
- Estimated payment = (total tax − withholding) ÷ 4; safe harbor = 100%/110% of prior-year tax. Federal only. Jurisdiction: United States, 2026.
How it is calculated
- Net earnings = net profit × 92.35%. SE tax = 12.4% × min(net earnings, $184,500 − W-2 wages) + 2.9% × net earnings + 0.9% over $200,000.
- AGI ≈ profit + other income − ½ SE tax. Taxable income = AGI − standard deduction − QBI (20% of the smaller of qualified income or taxable income before QBI).
- Total tax = income tax (2026 brackets) + SE tax. Quarterly = (total − withholding) ÷ 4, or the prior-year safe harbor ÷ 4.
Examples
| Net profit (single, 2026) | SE tax | Income tax | Total | Per quarter |
|---|---|---|---|---|
| $30,000 | $4,238.87 | $942.44 | $5,181.31 | $1,295.33 |
| $60,000 | $8,477.73 | $3,559.47 | $12,037.20 | $3,009.30 |
| $100,000 | $14,129.55 | $8,235.00 | $22,364.55 | $5,591.14 |
| $250,000 | $29,851.26 | $34,667.76 | $64,519.02 | $16,129.76 |
Common mistakes
- S corporation owners pay FICA on salary instead of SE tax on distributions; this tool is for Schedule C / partnership self-employment income.
- State estimated taxes (California 30/40/0/30 split, New York, etc.) are separate.
- Underpayment penalty is an interest charge (about 7–8% annualized in 2025–26) on each late or short installment, even if you get a refund.
FAQ
What is self-employment tax?
Social Security and Medicare for people who work for themselves: 15.3% of 92.35% of net profit (12.4% + 2.9%), because you pay both the employee and employer halves. It applies once net earnings reach $400. Half of it is deductible from income (Schedule 1), which is why the effective rate is about 14.1%. The Social Security part stops at $184,500 of combined wages and net earnings in 2026; Medicare has no cap and adds 0.9% above $200,000.
How much should I set aside per quarter?
This year's total federal tax (income tax + SE tax) minus withholding, divided by four, or the safe-harbor amount: 100% of last year's total tax (110% if last year's AGI exceeded $150,000) in four equal installments. Paying the safe harbor avoids the underpayment penalty even if your income jumps. Many freelancers set aside 25–30% of each payment.
When are 2026 estimated taxes due?
April 15, June 15 and September 15, 2026, and January 15, 2027 (Form 1040-ES). The periods are not equal (Q2 covers only two months). If a date falls on a weekend or holiday it moves to the next business day. State estimates have their own schedule.
What does this calculator leave out?
State income tax, the self-employed health insurance deduction, SEP-IRA or solo 401(k) contributions, itemized deductions, tax credits, and the wage/UBIA limits on the QBI deduction above $197,300 (single) of taxable income. It also assumes all income is ordinary. It is a planning estimate, not a return.