What Self-Employment Tax Actually Is
When you are an employee, your paycheck already splits the payroll tax: you pay 6.2% for Social Security and 1.45% for Medicare, and your employer pays a matching 6.2% and 1.45%. Self-employed people owe both halves — that combined 15.3% is the self-employment (SE) tax.
The SE tax is separate from your regular income tax. You can owe $0 in federal income tax (because of the standard deduction and business write-offs) and still owe a four-figure SE tax bill. That surprise is the #1 thing new freelancers miss.
- SE tax = 12.4% Social Security + 2.9% Medicare = 15.3% total in 2026.
- It applies to your net self-employment earnings, not your gross revenue.
- It is on top of — not instead of — your income tax.
The 2026 Numbers That Decide Your Bill
Three figures drive almost every SE tax calculation this year:
Social Security wage base: $184,500
The 12.4% Social Security portion only applies up to the wage base. For 2026 that cap is $184,500 of net earnings. Earn more than that from self-employment and the Social Security part stops — but the 2.9% Medicare part never stops.
Additional Medicare Tax: 0.9% over $200,000
On top of the 2.9% Medicare tax, a 0.9% Additional Medicare Tax kicks in on earnings above $200,000 (single) — $250,000 if married filing jointly. So high earners effectively pay 3.8% Medicare above the threshold.
The 92.35% factor
You do not pay SE tax on every dollar of profit. The IRS lets you multiply net earnings by 0.9235 first, because a hypothetical employer "share" is treated as a business expense. This 7.65% haircut is built into every SE tax worksheet.
Net earnings = profit after ordinary business expenses. A $50,000 profit is taxed on $46,175 ($50,000 x 0.9235), not on the full $50,000.
Worked Example: A $60,000 Freelance Profit
Say a sole proprietor has $60,000 of net self-employment earnings in 2026.
Step 1 — apply the 92.35% factor: $60,000 x 0.9235 = $55,410 of SE taxable earnings.
Step 2 — Social Security (12.4%, capped at $184,500): $55,410 x 0.124 = $6,871.
Step 3 — Medicare (2.9%, no cap, and under the $200,000 threshold so no extra 0.9%): $55,410 x 0.029 = $1,607.
Total SE tax = $8,478. That is about 14.1% of the original $60,000 profit — slightly under 15.3% because of the 92.35% factor.
- SE taxable base = net profit x 0.9235.
- Social Security maxes out at $184,500 of that base ($22,878 in 2026).
- Medicare is uncapped and adds 0.9% above the threshold.
The Deduction That Gives Half Back
Here is the rule that softens the blow: you can deduct one-half of your SE tax as an above-the-line deduction. It lowers your adjusted gross income and therefore your income tax, but it does not reduce the SE tax itself.
In the example above, half of $8,478 = $4,239 is deductible. It is entered on Schedule 1 (Form 1040), not on Schedule SE.
The 50% deduction reduces your income tax, not your SE tax. Do not subtract it before computing the SE tax or you will underpay.
Quarterly Estimated Payments — Pay As You Go
There is no employer withholding SE tax for you. The IRS expects you to pay it in four estimated installments (Form 1040-ES) roughly on April 15, June 15, September 15, and January 15. If you underpay during the year, you owe a penalty at filing even if you pay the full balance by April.
A simple safe harbor: if your total annual withholding and estimated payments cover 100% of last year's tax (110% if your AGI was over $150,000), you avoid the underpayment penalty regardless of this year's actual bill.
Two Write-Offs That Lower the Base
Because SE tax is computed on profit, anything legitimate you deduct from your business also lowers your SE tax. Two are especially valuable to solo workers:
The standard mileage rate — 70 cents per mile for January 1 through June 30, 2026, rising to 76 cents per mile from July 1, 2026 — turns business driving into a direct reduction of taxable profit. And retirement contributions to a Solo 401(k) (up to $24,500 in 2026, plus catch-up) or a SEP IRA lower both your income tax and your SE tax base.
- Every legitimate business deduction lowers your SE tax base, not just your income tax.
- Track business miles — the mid-year rate jump to 76 cents matters for second-half driving.
- Solo 401(k) and SEP IRA contributions are double winners: they cut AGI and the SE base.
Frequently Asked Questions
Do I owe SE tax if I only made a little money?
You owe SE tax only if your net earnings from self-employment are $400 or more for the year. Below that, no SE tax is due, though you may still file a return for other reasons.
Is the $184,500 Social Security cap per job or total?
It is a total cap on your combined Social Security wages and SE earnings for 2026. If a W-2 job already pushed you past $184,500, your side self-employment income is not subject to the 12.4% Social Security portion (though Medicare still applies).
Can I just pay SE tax once a year?
You can, but you will likely owe an underpayment penalty. The IRS expects quarterly estimated payments; the safe harbor is covering 100% of the prior year's tax (110% above $150,000 AGI).
Does the Qualified Business Income (QBI) deduction reduce SE tax?
No. The QBI deduction reduces your taxable income (up to 20% of qualified business income) and therefore your income tax, but it is computed after SE tax and does not lower the SE tax itself.