Illinois Income Tax Calculator 2026

How Illinois Income Tax Calculator Works

Calculate your Illinois income tax (4.95% flat rate) plus federal tax. See combined brackets, effective rate, and take-home pay. Enter your values into the form above and the calculator processes them instantly in your browser — no data is sent to any server.

Illinois Income Tax: 4.95% Flat Rate

Illinois uses a flat income tax rate of 4.95% (35 ILCS 5/201), meaning all taxable income is taxed at the same rate regardless of how much you earn. Illinois has no standard deduction; instead each taxpayer and dependent gets a $2,925 personal exemption for 2026, which is not available above $250,000 of income ($500,000 joint). Illinois has a constitutionally mandated flat tax. A 2020 ballot measure to allow graduated rates was defeated by voters.

On top of the 4.95% state tax, Illinois residents also pay federal income tax ranging from 10% to 37%. This calculator combines both federal and Illinois state tax to show your total liability, effective rate, and take-home pay.

How Illinois's Flat Tax Compares

A flat tax simplifies filing — you pay 4.95% on all taxable income without navigating multiple brackets. For a single filer earning $60,000, Illinois tax is about $2,825 (4.95% of $57,075 after the $2,925 exemption); at $100,000 it is about $4,805.

States with flat taxes tend to have simpler returns and more predictable tax bills. The trade-off is that lower-income residents pay the same percentage as higher earners, unlike graduated systems where rates increase with income.

Reducing Your Illinois Tax Bill

While you cannot change the flat rate, you can reduce your taxable income. Contributions to traditional 401(k) and IRA accounts reduce both your federal and Illinois state taxable income. The 2026 401(k) limit is $24,500 ($32,500 with catch-up for age 50+). HSA contributions are also pre-tax for both federal and state purposes in most states.

Tips for Getting Accurate Results

For the most accurate results, use up-to-date numbers from official sources. Double-check your inputs before calculating — small errors in the starting values can lead to significantly different outputs. If you are comparing scenarios, keep all variables the same except the one you are testing. Save or screenshot your results for future reference. This calculator uses standard formulas and is designed to give you a reliable quick estimate, though professional advice may be needed for complex situations.