Illinois Income Tax

Illinois uses a flat income tax rate applied to all taxable income. Combined with federal tax, this determines your total income tax burden.

Why It Matters

Understanding Illinois's income tax structure helps you accurately estimate take-home pay, compare compensation across states, and plan for your total tax burden.

Try the calculator

Open Illinois Income Tax Calculator →

How It Works

The calculator computes both your federal and Illinois state income tax to show your combined tax burden. Enter your taxable income to see the breakdown.

Example

Single filer • $100,000 taxable income • 2025

Federal

$16,914

16.91%

Illinois

$4,950

4.95%

Combined

$21,864

21.86%

Resources

Illinois Tax Authority

Official Illinois state tax information, forms, and filing resources.

Source: Illinois Department of Revenue

Frequently Asked Questions

Does Illinois have a standard deduction?

Illinois's deduction rules vary. Some flat-tax states conform to the federal standard deduction, while others have their own. Check your state tax authority for details.

Is Illinois's income tax in addition to federal tax?

Yes. You pay both federal income tax (progressive brackets up to 37%) and Illinois's flat 4.95% state income tax. This calculator shows both combined for your total tax burden.

What is Illinois's income tax rate?

Illinois has a flat income tax rate of 4.95% applied to all taxable income regardless of how much you earn.

Key Terms

Effective Tax Rate

The average rate you actually pay across all your income — total tax divided by total income.

Filing Status

A category that determines your tax bracket thresholds, standard deduction, and eligibility for certain credits.

Marginal Tax Rate

The tax rate applied to your next dollar of income — the highest bracket you've reached.

Modified Adjusted Gross Income

Your adjusted gross income (AGI) with certain deductions added back, used to determine eligibility for tax benefits and surtaxes like the NIIT.

Standard Deduction

A fixed amount subtracted from gross income before tax brackets are applied — used by about 90% of filers.

Taxable Income

Your gross income minus deductions — the amount used to determine which tax bracket you fall into.

Next review: 2027-01-15 • Applies to tax year: 2025