Self-Employment Tax, Explained
Educational explainer, not tax advice — every figure below is computed for 2026 by the same tested engine that powers this site's calculators. Federal taxes only; state and local taxes are out of scope.
The first self-employed year usually contains one genuine shock, and it is not the income tax — it is the tax that W-2 paychecks kept invisible. This guide explains what self-employment tax is, why it applies to 92.35% of profit rather than all of it, where the Social Security wage base caps it, what the deductible half actually does, and how the quarterly payment rhythm replaces withholding — with one 2026 example traced end to end through the engine.
One tax, both halves
Self-employment tax is Social Security and Medicare — the same programs employees fund through FICA — collected in full from one person. An employee pays 6.2% Social Security and 1.45% Medicare, 7.65% together, and the employer silently matches it. Self-employment merges both roles, so the combined rate is 12.4% Social Security plus 2.9% Medicare — 15.3% in all. It is owed on top of federal income tax, not instead of it: the two are computed separately and added, as the worked example below shows. The Self-Employment Tax Calculator runs this computation for any earnings level.
The 92.35% multiplier, honestly
SE tax is not charged on all of net earnings. Schedule SE first multiplies net self-employment earnings — the Schedule C profit, revenue minus expenses — by 92.35%, and the tax applies to that base. The multiplier is exactly 100% minus 7.65%: it removes the equivalent of the employer half of FICA from the base, because an employee's FICA wages never include the employer's share of payroll tax either. It is a flat statutory adjustment rather than a precise accounting, but its effect is real: on the $80,000 example below, SE tax works out to 14.13% of profit rather than the headline 15.3%.
A worked example, end to end
$80,000 of net self-employment earnings, single filer, standard deduction, no other income — every line computed by the engine:
| Step | Amount |
|---|---|
| Net earnings (Schedule C profit) | $80,000 |
| SE tax base — 92.35% of net earnings | $73,880.00 |
| Social Security — 12.4% of the base (under the cap) | $9,161.12 |
| Medicare — 2.9% of the base | $2,142.52 |
| Self-employment tax | $11,303.64 |
| Deductible half (an income-tax deduction) | $5,651.82 |
| Taxable income after that half and the $16,100 standard deduction | $58,248.18 |
| Federal income tax on that | $7,526.60 |
| Combined federal total (SE tax + income tax) | $18,830.24 |
The order matters: SE tax is computed first, directly from profit, and the deductible half then shrinks only the income-tax side of the ledger. Nothing about the deduction feeds back into the SE tax itself.
The Social Security wage base
The Social Security portion stops at an annual ceiling set by the Social Security Administration — $184,500 for 2026. The cap applies to the SE tax base, so in profit terms it is reached at about $199,783 of net earnings ($184,500 ÷ 92.35%). Medicare has no ceiling. At $250,000 of net earnings, the engine computes $22,878.00 of Social Security — capped — while Medicare continues on the full base at $6,695.37, plus $277.88 of the 0.9% Additional Medicare surtax on the base above $200,000. The surtax threshold varies by filing status ($250,000 married filing jointly, $125,000 married filing separately, per the Form 8959 instructions); this site's engine estimates it at the $200,000 single-filer threshold.
What the deductible half does — and does not — reduce
Half of the SE tax comes back as an above-the-line income-tax deduction, mirroring an employer's ability to deduct its share of payroll tax as a business expense. Precisely, the deductible half is half of the Social Security and 2.9% Medicare portions — the 0.9% surtax is not deductible and is excluded from the half entirely. In the high-earner example, the deduction is $14,786.69 — half of $22,878.00 plus $6,695.37 — while the $277.88 surtax stays outside it. And the deduction reduces taxable income for the income-tax computation only: it does not reduce the SE tax, which is figured first, and it does not reduce the surtax.
The quarterly rhythm
No one withholds tax from 1099 income, so the rules collect it as the year progresses: Form 1040-ES estimated payments, due on four dates — for 2026, April 15, 2026; June 15, 2026; September 15, 2026; January 15, 2027. The required annual payment is the lesser of 90% of the current year's expected tax or 100% of the prior year's tax (110% when prior-year AGI exceeds $150,000), and no installments are required at all when the expected balance after withholding is under $1,000. For the example earner, the 90% harbor works out to $4,236.80 per installment, with the remainder settled at filing. The Quarterly Tax Calculator applies these rules to any mix of self-employment and W-2 income.
1099 vs. W-2, conceptually
The same work funds the same programs either way; what changes is visibility and timing. A W-2 employee sees 7.65% of FICA leave each paycheck, never sees the employer's matching half, and has income tax withheld automatically — the Take-Home Pay Calculator shows that side of the ledger. A 1099 contractor is paid gross: both FICA halves surface as SE tax, income tax arrives as quarterly estimates rather than withholding, and the half-deduction restores the business-expense treatment an employer gets for its share. The dollars are more visible, not necessarily larger — which is much of why the same burden feels heavier in the first self-employed year.
Frequently asked questions
Is self-employment tax instead of federal income tax?
No — it is in addition. Self-employment tax funds Social Security and Medicare; federal income tax is computed separately on taxable income after the deductible half of SE tax comes off. In the worked example, $80,000 of net earnings produces $11,303.64 of SE tax plus $7,526.60 of income tax for a single filer taking the standard deduction.
Why is the rate 15.3% when employees see 7.65%?
Employees split the same taxes with an employer: each side pays 6.2% Social Security and 1.45% Medicare. Self-employment means covering both sides — 12.4% plus 2.9% — with the employer-equivalent half returned as an income-tax deduction.
Does the deductible half reduce the self-employment tax itself?
No. The deduction reduces taxable income for the income-tax computation only — the SE tax is figured first and does not change. The deductible half is half of the Social Security and 2.9% Medicare portions; the 0.9% Additional Medicare surtax is excluded from it entirely.
Does a small side income owe self-employment tax?
The statutory floor is $400 of net self-employment earnings — below that, Schedule SE is not required at all (per the IRS Schedule SE instructions). At $400 and above, the tax applies to the full computed base, not just the amount over the floor.
Not tax advice: an educational explainer of the federal core. It excludes state and local taxes, the $400 statutory floor below which SE tax does not apply, coordination of the wage base with W-2 wages earned in the same year, filing-status differences in the 0.9% surtax threshold, the optional methods for low-income years, and entity-structure effects (an S-corp changes this math). Every figure above is computed at build time from the 2026 data file by the same tested engine as the calculators. Consult a tax professional for your situation. See the methodology page.