How Illinois income tax works
Illinois taxes individual income with a single flat rate of 4.95%.
Your tax is calculated on taxable income — gross income minus the $2,775 standard deduction for a single filer.
Flat 4.95% rate with a personal exemption rather than a standard deduction.
Illinois income tax rates for 2026
Every dollar of taxable income is taxed at 4.95%, so your marginal and average rates are the same before deductions.
Your effective rate is the total tax divided by your gross income; your marginal rate is the rate on your next dollar earned. The calculator shows both.
Illinois taxes capital gains as ordinary income at the flat 4.95% rate.
Lowering your Illinois tax bill
Pre-tax contributions to retirement accounts, health savings accounts and other deductions reduce the taxable income this calculator starts from.
Remember this estimate covers IL state income tax only. Federal income tax and payroll taxes apply on top, and this is a planning estimate — verify with the Illinois Department of Revenue (tax.illinois.gov) or a tax professional.
Frequently asked questions
How much is Illinois state income tax?
Illinois charges a flat 4.95% on taxable income.
What is the difference between effective and marginal rate?
Your marginal rate is the rate on your last dollar of income; your effective rate is your total tax divided by total income, which is lower because of brackets and deductions.
Does this include federal tax?
No. This calculator estimates IL state income tax only. Federal income tax and payroll taxes are separate and apply on top.
How are capital gains taxed in Illinois?
Illinois taxes capital gains as ordinary income at the flat 4.95% rate.