Illinois Income Tax Calculator
Illinois is one of a minority of states that levies a flat income tax, meaning every dollar of net income is taxed at the same rate: 4.95% for tax year 2024. There are no brackets, no graduated rates, and no difference in rate between high and low earners. Illinois income tax is applied to your net income, which begins with federal adjusted gross income (AGI) and is adjusted for Illinois-specific additions and subtractions. A personal exemption of $2,425 (for qualifying taxpayers under $250,000 net income) further reduces the tax base. Enter your Illinois net income (after exemptions) to estimate your state income tax.
Illinois income tax formula
IL Tax = Net Income x 0.0495
Illinois applies a single flat rate of 4.95% to all net income. The personal exemption ($2,425 for 2024, for eligible taxpayers) should be subtracted from net income before applying this rate. Enter the net income after the exemption for the most accurate result.
What makes Illinois unique among state income taxes?
Most states use graduated brackets where higher income is taxed at higher rates. Illinois's constitution requires a flat tax rate for all residents, so a worker earning $30,000 and one earning $300,000 pay exactly the same percentage. Illinois has voted on constitutional amendments to allow graduated rates, most recently in 2020 (Proposition 1), but the amendment failed.
Illinois also exempts substantially all retirement income, making it attractive for retirees despite its flat rate applying to wage income.
Illinois income tax FAQ
What is Illinois's income tax rate?
Illinois levies a flat income tax rate of 4.95% on net income for individuals. Unlike most states, Illinois does not use graduated brackets. All taxable income is taxed at the same 4.95% rate regardless of how much you earn.
What is Illinois net income for tax purposes?
Illinois net income starts with your federal adjusted gross income, then adds back certain items not allowed under Illinois law and subtracts Illinois-specific deductions. Common additions include interest income from other states' bonds. Common subtractions include Social Security income and certain retirement income.
Does Illinois have a personal exemption?
Yes. Illinois allows a personal exemption of $2,425 per taxpayer for 2024 (for taxpayers with net income under $250,000). This exemption is claimed on Schedule IL-E/EIC and reduces your taxable Illinois net income.
Does Illinois tax retirement income?
Illinois exempts most retirement income, including Social Security benefits, military retirement pay, and distributions from 401(k) and pension plans, from state income tax. This is one of the most retirement-friendly provisions in the state.
Where do I file Illinois income tax?
Illinois individual income tax is filed on Form IL-1040 with the Illinois Department of Revenue (IDOR). The filing deadline matches the federal deadline, typically April 15. Illinois offers free e-filing through the MyTax Illinois portal at mytax.illinois.gov.
Official sources
- Illinois Department of Revenue: Individual Income Tax.
- Illinois Form IL-1040 Instructions: IL-1040 Instructions.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.