What is the self-employment tax rate?

Self-employment tax is 15.3% — 12.4% for Social Security plus 2.9% for Medicare — applied to 92.35% of your net self-employment earnings. Social Security stops at the annual wage base; the 2.9% Medicare portion has no cap.

Why is only 92.35% of income taxed?

The 92.35% factor (1 minus half of the 15.3% rate) approximates the employer-side payroll tax that employees do not pay on their wages, so the self-employed are not taxed on the tax itself. It is built into Schedule SE.

How does Illinois tax self-employment income?

Illinois applies its flat 4.95% rate to your net self-employment income after the federal deduction for one-half of SE tax and the personal exemption. There are no graduated brackets, so the state portion is straightforward.

Can I deduct half my self-employment tax?

Yes. You can deduct one-half of your self-employment tax as an above-the-line adjustment on your federal return, which also lowers your Illinois base income. The calculator subtracts this half before applying the 4.95% state rate.

Do I need to make quarterly payments?

Generally yes. If you expect to owe 1,000 dollars or more in federal tax, the IRS requires quarterly estimated payments, and Illinois has its own quarterly schedule. Use this estimate to size those payments and avoid underpayment penalties.

Illinois Self-Employment Tax Calculator

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Working for yourself in Illinois means you owe two layers of tax that an employee’s paycheck handles automatically: the federal self-employment (SE) tax that covers both halves of Social Security and Medicare, and Illinois state income tax at the flat 4.95% rate. This calculator combines them, applies the standard 92.35% adjustment and the deductible half of SE tax, so you can size your quarterly estimated payments accurately.

How it works

The calculation mirrors Schedule SE and the Illinois return:

Net earnings subject to SE tax. Multiply your net profit by 92.35% to remove the employer-equivalent portion: seBase = netProfit × 0.9235.
Self-employment tax. Apply 12.4% Social Security up to the wage base and 2.9% Medicare with no cap: seTax = seBase × 0.153 (the Social Security part stops above the wage base).
Half-SE deduction. Deduct one-half of the SE tax from income for both federal and Illinois purposes.
Illinois state tax. Subtract the half-SE deduction and your personal exemption from net profit, then apply 4.95%.

The result is your combined federal SE tax plus Illinois income tax on the same self-employment income.

Tips and example

On $80,000 of net profit, 92.35% is $73,880. Self-employment tax at 15.3% is about $11,304. Half of that ($5,652) is deductible, so Illinois taxes roughly $80,000 − $5,652 − $2,850 exemption = $71,498 at 4.95%, about $3,539. Your combined SE plus Illinois bill is roughly $14,843 — before any federal income tax.

Remember this tool covers SE tax and Illinois state tax; your federal income tax is separate and depends on your full return. Set aside enough each quarter to cover all three. Above the Social Security wage base, only the 2.9% Medicare portion continues, which lowers your marginal SE rate.