What is the Illinois income tax rate?

Illinois charges a single flat rate of 4.95% on net taxable income. Unlike most states, it has no graduated brackets — every dollar of taxable income is taxed at the same 4.95% whether you earn 30,000 dollars or 300,000 dollars.

Does Illinois have a standard deduction?

No. Illinois has no standard deduction or itemized deductions. The only major subtraction for most filers is the personal exemption — about 2,850 dollars per person for 2025 — claimed for the taxpayer, spouse and each dependent.

Is retirement income taxed in Illinois?

No. Illinois does not tax Social Security, qualified pensions, or distributions from IRAs and 401(k) plans. Those amounts are subtracted from federal income when computing Illinois base income, so they are excluded from the 4.95% rate.

What is Illinois base income?

Illinois starts from your federal adjusted gross income, then adds back certain items (like federally tax-exempt bond interest) and subtracts others (retirement income, U.S. Treasury interest) to reach base income, which the exemption is taken from.

Does the exemption ever phase out?

Yes. The personal exemption is not allowed once income exceeds roughly 250,000 dollars for single filers or 500,000 dollars for joint filers. Above those thresholds the flat 4.95% applies to your full base income.

Illinois Income Tax Calculator

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Illinois keeps its state income tax refreshingly simple: a single flat rate of 4.95% applies to everyone, with no brackets to track and no standard deduction to claim. The main thing that reduces your bill is the personal exemption, which you claim for yourself, your spouse and each dependent. This calculator applies that exemption and the flat rate to show exactly what you owe Illinois.

How it works

Illinois income tax is deliberately straightforward:

Base income. Start from your Illinois base income — federal adjusted gross income adjusted for Illinois additions (e.g. tax-exempt bond interest) and subtractions (e.g. retirement income, U.S. Treasury interest).
Exemption allowance. Multiply your number of exemptions by the per-person amount (about $2,850 for 2025) and subtract it from base income. The result is net taxable income.
Tax. Apply the flat 4.95% rate: tax = net taxable income × 0.0495.

Because the rate never changes, your marginal and average rates converge toward 4.95% as income rises and the fixed exemption shrinks as a share of income.

Tips and example

A single filer with $70,000 of base income and one exemption subtracts $2,850, leaving $67,150 taxed at 4.95% — about $3,324, an effective rate of roughly 4.75% of total income.

A married couple with two children claims four exemptions (4 × $2,850 = $11,400). On $120,000 of base income that leaves $108,600 taxable, or about $5,376 in Illinois tax. Remember that the exemption disappears above $250,000 (single) or $500,000 (joint), so high earners pay the full 4.95% on all base income. This estimates state tax only — federal tax and FICA are separate.