Find out exactly what you'll take home. Our free calculator handles the Illinois flat 4.95% state tax, federal withholding, FICA, and all your pre-tax deductions — instantly.
Each allowance reduces taxable income by $2,925/year (2025 rate)
This calculator provides estimates for informational purposes. Consult a tax professional for advice specific to your situation. Calculations reflect 2025 Illinois and federal tax rates.
Illinois has one of the simplest state tax systems in the country. Here's exactly what comes out of your paycheck every pay period.
Illinois taxes all income at a single flat rate of 4.95% — no brackets, no tiers. Whether you earn $30,000 or $300,000, the same percentage applies. Each IL-W-4 allowance reduces your taxable income by $2,925/year (2025 rate), lowering your withholding.
Federal taxes use progressive brackets from 10% to 37%. The amount withheld depends on your W-4 filing status (Single, Married, Head of Household), dependents claimed, and additional withholding requests. The 2020+ W-4 redesign no longer uses traditional allowances.
All employees pay 6.2% for Social Security (on earnings up to $176,100 in 2025) and 1.45% for Medicare on all earnings. Earners above $200,000 pay an extra 0.9% Medicare surtax. Your employer matches both Social Security and Medicare.
Unlike neighboring states, no Illinois city or county levies a local income tax. Chicago, Springfield, Rockford — none of them add extra tax on top of the state rate. This makes calculating your Illinois paycheck significantly simpler than states like Pennsylvania or Ohio.
Contributions to a 401(k), 403(b), HSA, or FSA are deducted before taxes are calculated. This means they reduce both your federal and Illinois state taxable income, making them one of the most powerful ways to increase your take-home pay legally.
Illinois has reciprocal tax agreements with Iowa, Kentucky, Michigan, and Wisconsin. If you live in one of those states but work in Illinois, your Illinois wages are exempt from Illinois state income tax withholding — you only pay taxes to your home state.
| Tax Type | Rate | Applies To | Wage Limit |
|---|---|---|---|
| Illinois State Income Tax | 4.95% | All Illinois wages (after exemptions) | No limit |
| Federal Income Tax | 10%–37% | Taxable wages (progressive brackets) | No limit |
| Social Security (OASDI) | 6.2% | Employee wages | $176,100 |
| Medicare (HI) | 1.45% | All wages | No limit |
| Additional Medicare Tax | 0.9% | Single filers above $200k | No limit |
| Illinois Minimum Wage | $15.00/hr | Most employees | State floor |
Source: Illinois Department of Revenue, IRS Publication 15-T, Booklet IL-700-T (2025). Rates are subject to annual change.
Illinois applies a flat 4.95% income tax rate to all taxable income. This flat-tax structure means there are no brackets — every dollar of taxable income is taxed at the same rate, making Illinois one of the simplest states to calculate paycheck withholding for.
No. Illinois has no city or county income taxes, unlike many other states. Whether you work in Chicago, Aurora, Naperville, or anywhere else in Illinois, your only state-level obligation is the 4.95% flat tax.
For the 2025 tax year, each allowance on your Form IL-W-4 reduces your taxable income by $2,925 per year (or proportionally per pay period). Additional exemptions apply if you are 65 or older or legally blind. You can also claim additional allowances for each dependent.
No. Illinois has reciprocal tax agreements with Iowa, Kentucky, Michigan, and Wisconsin. Residents of these states who earn wages in Illinois are exempt from Illinois state income tax withholding. You would file and pay income tax only in your home state.
Pre-tax 401(k) contributions reduce your federal taxable income and your Illinois taxable income. For example, contributing $500/month pre-tax saves you approximately $24.75/month in Illinois state tax alone (4.95% × $500), in addition to federal savings. Enter your annual contribution in the calculator above to see the exact impact.
The Social Security (OASDI) taxable wage base for 2025 is $176,100. Once your earnings exceed this threshold in a calendar year, the 6.2% Social Security withholding stops. Medicare tax (1.45%) continues on all wages with no cap.
Yes, if you enter your effective total earnings including overtime. Illinois follows federal overtime law, requiring time-and-a-half pay (1.5× hourly rate) for hours worked beyond 40 in a workweek. For hourly users, multiply your expected overtime hours by 1.5× your rate and include this in your weekly total before calculating.