Self-employment tax, explained — where 15.3% comes from and what softens it

Every employee pays Social Security and Medicare tax; they just never see most of it. The paycheck shows 7.65% coming out — and an identical 7.65% leaves the employer’s account without ever appearing on the stub. Become self-employed and the disguise drops: you are both parties now, and the combined 15.3% arrives under its own name, “self-employment tax,” on a return that used to hide it. Nothing new was invented for freelancers; the employee arrangement was simply two people splitting the same bill.

The actual mechanics, step by step

Start with net profit — your 1099 and business income minus business expenses. Then:

Step 1: multiply by 92.35%. This produces “net earnings from self-employment.” The odd factor is the system’s rough apology for the employer-half issue: employees don’t pay payroll tax on their employer’s share of payroll tax, so the self-employed get 7.65% shaved off the base first. If the result is under $400, self-employment tax doesn’t apply at all — the floor that keeps one-off odd jobs out of the system.

Step 2: Social Security, 12.4% — but capped. The 12.4% applies only up to the annual wage base: $184,500 in 2026. Income above the cap pays no Social Security tax, which is why SE tax’s bite falls at high incomes. Critically for moonlighters: W-2 wages consume the wage base first. If your job pays $150,000, only $34,500 of freelance earnings face the 12.4%; a salary above the base zeroes it out entirely, leaving just Medicare on the side income. This is the single most common over-estimate in DIY freelancer math — the calculator does the wage-base offset automatically.

Step 3: Medicare, 2.9% — uncapped, plus a surcharge. Medicare’s 2.9% applies to every dollar of net earnings, and an Additional Medicare Tax of 0.9% starts once wages plus self-employment income cross $200,000 (single or head of household; $250,000 married-joint, $125,000 married-separate). Employers must withhold the extra 0.9% above $200,000 of wages regardless of your actual filing situation, so two-earner couples sometimes reconcile a gap at filing.

Step 4: deduct half of it. Half your SE tax comes back off the top of your income as an adjustment — the deduction that mirrors how an employer’s half was never the employee’s income. It reduces income tax, not the SE tax itself, but at a 22–24% bracket it’s real money: on $8,000 of SE tax, roughly $900–1,000 of income tax saved.

What it looks like in dollars

A single freelancer with $60,000 net profit and no other income, using 2026 figures: net earnings are $55,410; Social Security takes $6,871, Medicare $1,607 — $8,478 of SE tax — and $4,239 comes back as the half-deduction before income tax is figured. Total federal bill: about $12,037, of which SE tax is 70%. That proportion is the story for most middle-income freelancers: SE tax, not income tax, is the bigger check, because it starts at dollar one with no standard deduction to shield it.

(Those numbers are the live output of this site’s engine for that exact input — type $60,000 into the calculator and open “See the full math” to watch each step land.)

What it buys — this is not a void

Unlike income tax, SE tax is hypothecated: the 12.4% funds your own Social Security record. Your self-employment earnings post to your account exactly as wages would, accumulating the same retirement and disability credits. A freelancer who under-reports income to dodge SE tax is also quietly shrinking their own retirement benefit — the seldom-mentioned second edge of that particular knife. The 2.9% likewise funds your Medicare eligibility at 65.

Legitimate ways it gets smaller

Business expenses are the honest first lever: every deductible dollar avoids SE tax and income tax together — worth 30–40 combined percentage points for many filers. The deductions checklist is the practical tour.

The W-2 offset, above, if you also have a job — automatic, not elective.

An S-corp election, eventually. Profit paid out as S-corp distributions (after a reasonable salary) escapes SE tax — a real saving with real costs and an IRS-watched “reasonable salary” requirement. The arithmetic starts mattering at sustained high-five-figure profits; the entity guide does it honestly.

What doesn’t work: the QBI deduction reduces income tax only — SE tax is figured before it; and an LLC by itself changes nothing (a single-member LLC files the same Schedule C). Retirement contributions likewise reduce income tax but not SE tax.

The mindset correction

The scary version — “freelancers pay 15.3% extra!” — overstates in three ways: the 92.35% multiplier trims the base; the half-deduction refunds a slice through income tax; and the wage-base cap plus your expense deductions shrink what the rate touches. The SE tax itself on our $60,000 example is about 14.1% of profit — effectively less once the half-deduction’s income-tax refund is counted — and it funds your own benefits. It’s a real cost worth planning around — quarterly, with the estimator — but it’s a payroll tax you finally get to see, not a penalty for working for yourself.

Figures are 2026, compiled July 2026 from IRS and SSA sources (methodology). General information, not advice for your situation.