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How Self-Employment Tax Works in Illinois (2026)
Self-employment tax is 15.3% — 12.4% Social Security plus 2.9% Medicare — applied to 92.35% of your net self-employment income, on top of federal and Illinois income tax. Half of the SE tax (7.65% equivalent) is an above-the-line deduction against your federal taxable income.
| Piece | Rate / rule |
|---|---|
| Net earnings subject to SE tax | 92.35% of net profit |
| Social Security portion | 12.4% (up to $184,500 of net earnings) |
| Medicare portion | 2.9% · +0.9% above $200,000 |
| Deductible half of SE tax | 50%, above-the-line on your federal return |
Estimated payments are due quarterly (roughly mid-April, mid-June, mid-September, and mid-January). The 20% Qualified Business Income deduction (§199A) is not modeled here — it depends on your income level and business type. If you also have W-2 wages, the Social Security cap is measured against your combined earnings, so this estimate runs high.
Illinois Self-Employment Tax by Income (2026)
Single filer, 1099 income is the only earnings for the year. The quarterly figure is an even 4-way split of the annual total.
| Net 1099 income | SE tax | Federal tax | Illinois tax | Quarterly payment |
|---|---|---|---|---|
| $20,000 | $2,826 | $249 | $800 | $969 |
| $40,000 | $5,652 | $2,281 | $1,720 | $2,413 |
| $60,000 | $8,478 | $4,511 | $2,640 | $3,907 |
| $80,000 | $11,304 | $7,527 | $3,560 | $5,598 |
| $100,000 | $14,130 | $11,616 | $4,480 | $7,556 |
Illinois Self-Employment Tax FAQ
How much is self-employment tax in Illinois?
15.3% federal SE tax on 92.35% of net profit (12.4% Social Security up to $184,500, 2.9% Medicare), plus Illinois's flat 4.95% income tax on net profit, plus federal income tax. Half the SE tax is deductible federally.
Do 1099 workers pay quarterly taxes in Illinois?
Yes - federal estimates if you will owe $1,000 or more, and Illinois estimates once your unpaid state tax passes its threshold (check the Illinois Department of Revenue), on the standard mid-April / mid-June / mid-September / mid-January schedule.
Does Illinois have its own self-employment tax?
No - the 15.3% SE tax is federal. Illinois taxes your net self-employment profit at its 4.95% flat rate. Illinois does not allow the federal QBI deduction, so full net profit is taxed for state purposes.
Methodology & Source
Illinois state tax figures sourced from Illinois Department of Revenue (https://tax.illinois.gov/), citing 35 ILCS 5/201 — flat 4.95% rate (Illinois Constitution art. IX, § 3 prohibits graduated rates). Federal brackets, standard deductions (single/MFJ/HoH), and FICA constants sourced from the IRS (Revenue Procedure 2025-32; married-filing-jointly Additional Medicare threshold of $250,000 is a separate, unindexed statutory figure). Illinois's married-filing-jointly and head-of-household figures have been independently verified against the source above.
Self-employment tax uses the statutory 15.3% rate (12.4% Social Security + 2.9% Medicare) on 92.35% of net self-employment income, with half of the SE tax deducted from federal taxable income above-the-line — per IRS Schedule SE (Form 1040) instructions, IRC §1401 and §164(f), 2026 edition. The 20% Qualified Business Income deduction (IRC §199A) is not modeled — it phases out by income and business type and is too state/entity-dependent to compute generically. This assumes the self-employment income is your only earnings for the year; if you also have W-2 wages, the Social Security wage-base cap and Additional Medicare threshold are actually based on your combined earnings, so this will overstate SE tax if you have significant wage income too.
This is an estimate based on standard single-filer federal, FICA, and IL state calculations. Actual withholding may differ based on your W-4 elections, pre-tax deductions (401k, health insurance), and other factors.
Guideline version: 2026-IL-v1 · Effective: 2017-07-01 · Last verified: 2026-07-26