Tax Bracket Calculator for Illinois (IL) — Free Calculator

Illinois Tax Brackets (2026)

Illinois uses a flat income tax system with a top marginal rate of 4.95% flat.

Illinois Bracket Structure

Flat 4.95% on all net income — Illinois constitution requires a flat income tax rate

Illinois is constitutionally required to have a flat income tax. A 2020 ballot measure to allow graduated rates was rejected by voters. The 4.95% rate applies to all income, and Illinois does not allow a personal exemption for higher earners.

Federal Tax Brackets Still Apply to Illinois Residents

Regardless of Illinois's state tax rules, all residents pay federal income tax. Federal brackets for 2024 range from 10% (on income up to $11,600 for single filers) to 37% (on income over $609,350). Your effective federal rate is typically well below the top marginal rate due to the graduated bracket structure.

Effective vs. Marginal Rate in Illinois

Your marginal rate is the rate on your last dollar of income. Your effective rate is your total tax divided by total income. For Illinois residents the marginal rate can reach 4.95% flat but most filers pay a lower effective rate. The median household income in Illinois is $72,205.

Data: Tax Foundation (2024), IRS Statistics of Income, US Census Bureau ACS 2023. Updated 2024–2025. Figures reflect state averages — consult a licensed CPA for personalized tax advice.

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Frequently Asked Questions

What tax brackets apply to Illinois residents?

Illinois has a flat income tax system. Flat 4.95% on all net income — Illinois constitution requires a flat income tax rate. Federal brackets also apply on top of the state tax.

What is the difference between marginal and effective tax rate in Illinois?

Your marginal rate is the rate on your highest dollar of income. Your effective rate is your total tax burden divided by total income. In Illinois, even if the top marginal rate is 4.95% flat, most residents pay a lower effective rate because lower income portions are taxed at lower brackets.

Does Illinois have different tax brackets for married filers?

Yes, Illinois typically has different bracket thresholds for single vs. married filing jointly filers. Married joint filers often have brackets approximately twice as wide, reducing the marriage penalty. Check the Illinois Department of Revenue for current bracket tables.

How does this tax bracket calculator work for Illinois?

Enter your income and filing status. The calculator applies both federal and Illinois state tax brackets to show your marginal rate, effective rate, and total estimated tax. Illinois's flat rate of up to 4.95% flat is applied to your state taxable income.