Self-Employment Tax Explained: The 15.3% Broken Down

Every W-2 employee pays into Social Security and Medicare through FICA tax, split 50/50 with their employer — 7.65% comes out of the paycheck, and the employer quietly pays a matching 7.65%. Self-employment tax exists because a freelancer has no employer to cover that other half — so the IRS collects both halves, 15.3% total, directly from you.

The 15.3% breakdown

• 12.4% — Social Security portion, applied up to an annual wage base limit that adjusts each year.
• 2.9% — Medicare portion, with no income cap at all.
• An additional 0.9% Medicare surtax applies to self-employment income above certain thresholds ($200,000 single / $250,000 married filing jointly), on top of the standard 2.9%.

How this compares to a W-2 paycheck

It helps to see the two side by side, because the total burden is identical — only who writes the check changes:

• W-2 employee: pays 7.65% (6.2% Social Security + 1.45% Medicare) through payroll withholding. The employer separately pays a matching 7.65% that never shows up on the employee's pay stub as income.
• Self-employed freelancer: pays the full 15.3% directly, since there's no employer to split it with. Nothing is withheld automatically — it's calculated and paid by you, typically through quarterly estimated payments.

This is the single biggest reason freelance income can feel more heavily taxed than a comparable salary. It isn't a higher tax rate — it's the same FICA burden, just with no employer absorbing half of it.

Why it's calculated on 92.35% of earnings, not 100%

Self-employment tax isn't applied to your full net profit — it's applied to 92.35% of net earnings. This adjustment exists because an employee's employer-paid FICA match isn't counted as the employee's taxable wage; the 92.35% factor roughly replicates that effect for the self-employed, so freelancers aren't taxed on a phantom "employer share" that doesn't really exist as separate income.

A full worked example

Say a freelance web developer nets $50,000 in self-employment profit for the year (revenue minus deductible business expenses, from Schedule C). Here's how the self-employment tax actually gets calculated, step by step:

1. Adjust for the 92.35% factor: $50,000 × 92.35% = $46,175 in net earnings subject to SE tax.
2. Apply the 12.4% Social Security portion: $46,175 × 12.4% = $5,726 (assuming total earnings stay under the annual Social Security wage base).
3. Apply the 2.9% Medicare portion: $46,175 × 2.9% = $1,339.
4. Add them together: $5,726 + $1,339 = $7,065 in total self-employment tax for the year.
5. Claim the deduction: half of that, about $3,533, is then deducted from taxable income before federal income tax is calculated — lowering the income tax bill on top of everything above.

Notice that self-employment tax alone — before any federal or state income tax is even calculated — comes to roughly 14% of this freelancer's net profit. That's why setting aside money throughout the year, not just at tax time, matters so much; see our guide to how much to save for taxes for a percentage-based approach to budgeting for it.

The half-SE-tax deduction

To further mirror how an employee's income tax isn't affected by their employer's FICA contribution, freelancers get to deduct half of their self-employment tax from their income before calculating federal income tax. This deduction is automatic on Schedule SE and doesn't require itemizing — it's taken directly on Form 1040 as an adjustment to income, so every freelancer gets it regardless of whether they take the standard deduction or itemize.

This is separate from income tax

Self-employment tax funds Social Security and Medicare specifically — it doesn't replace federal or state income tax, which is calculated separately on your total taxable income after deductions. Both apply together, which is why the percentage freelancers set aside for taxes needs to cover both, not just one. A freelancer in a moderate federal tax bracket can easily see a combined federal burden — self-employment tax plus income tax — of 25–35% of net profit, before any state income tax is added on top.

Common mistakes freelancers make with this tax

• Assuming an LLC eliminates it. Forming a single-member LLC doesn't change anything for self-employment tax by default — the IRS still taxes it as a sole proprietorship, and all net profit remains subject to the full 15.3%. Only electing S-Corp tax treatment changes the calculation, and even then, a "reasonable salary" portion still gets taxed the same way through payroll.
• Calculating it on gross revenue instead of net profit. Self-employment tax is owed on profit after business expenses, not on everything a client pays you. Track deductible expenses carefully — see our tax deduction checklist — since every dollar of legitimate deduction lowers this tax too, not just income tax.
• Forgetting it in quarterly payment estimates. It's easy to estimate quarterly payments based on income tax alone and forget self-employment tax entirely, leading to a much larger bill — and possibly an underpayment penalty — in April.
• Not realizing a loss year means no SE tax. If a freelance venture nets a loss for the year, no self-employment tax is owed on it, since the tax only applies to positive net earnings.

Why understanding this matters

Self-employment tax is close to a flat rate regardless of income level (aside from the Social Security wage base cap and the 0.9% surtax at high income), which makes it predictable to plan for. It's also why business structure decisions — like an S-Corp election — matter so much at higher income levels: only salary, not distributions, is subject to this tax under an S-Corp. For a freelancer netting $100,000, the difference between paying self-employment tax on the full amount versus on a $60,000 reasonable salary (with the remaining $40,000 taken as distributions) can mean thousands of dollars a year — though S-Corp status brings its own payroll and compliance costs that need to be weighed against the savings.

Frequently asked questions