Learn About Illinois State Income Tax Rates

Understanding Illinois State Income Tax Basics

Illinois has a state income tax system that applies to residents and certain non-residents who earn income within the state. The Illinois Department of Revenue administers these taxes and sets the rates that individuals and businesses must follow. Understanding how Illinois income tax works is foundational to managing your finances and meeting your tax obligations.

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Illinois taxes both wages from employment and other types of income, including interest, dividends, rental income, and self-employment income. The state uses a "flat tax" structure, which means the tax rate applies uniformly to most types of income rather than increasing based on how much you earn. This differs from the federal income tax system, which uses progressive tax brackets where higher earners pay higher percentages.

As of 2024, Illinois imposes a flat income tax rate of 4.95 percent on most personal income. This rate has remained consistent since 2017, when it was reduced from 5.25 percent. The flat rate applies to residents' income from all sources and to non-residents who earn income within Illinois. However, certain types of income may receive different treatment, and specific deductions and exemptions can reduce your taxable income.

Illinois residents who work in other states may still owe Illinois tax on their Illinois-source income, though they generally receive credit for taxes paid to other states to avoid double taxation. Non-residents who work in Illinois owe tax on their Illinois wages but not on income earned outside the state. Understanding which income counts as Illinois-source income is important for determining your tax liability.

Practical Takeaway: Illinois uses a flat 4.95 percent tax rate on most income types. Determine whether your income is considered Illinois-source income by examining where you work and where your income originates. This initial classification affects how much tax you owe and whether you need to file an Illinois state return.

State Income Tax Rates and Brackets

Unlike the federal government, Illinois does not use graduated tax brackets. Instead, the state applies a single tax rate to taxable income regardless of amount. The current flat rate of 4.95 percent means that a person earning $30,000 annually pays the same percentage rate as someone earning $300,000. This simplified structure makes calculating state tax liability more straightforward than federal calculations.

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The flat tax rate applies to wages, salaries, commissions, bonuses, tips, and other compensation from employment. It also applies to interest income from savings accounts and bonds, dividend income from stock investments, rental income from real estate, and net profit from self-employment or business activities. Capital gains—profits from selling investments or property—are also subject to the 4.95 percent rate.

Illinois tax law recognizes certain types of income as exempt from state taxation. Retirement income, including distributions from traditional and Roth IRAs, 401(k) plans, and pension plans, is not subject to Illinois income tax. This exemption applies regardless of the recipient's age or income level. Social Security benefits also remain exempt from Illinois state tax, providing additional tax relief for retirees.

Long-term capital gains—profits from holding investments for more than one year—received a significant tax change. Beginning in 2022, long-term capital gains became subject to a separate 20 percent tax rate in Illinois, rather than the standard 4.95 percent rate. This means if you sell appreciated investments you have held long-term, you owe a higher tax on those gains. However, short-term capital gains (from assets held less than one year) remain taxed at the 4.95 percent rate.

Municipal bonds issued by Illinois municipalities are exempt from Illinois state income tax, though they remain subject to federal income tax. This tax-exempt status makes Illinois municipal bonds attractive to state residents seeking tax-advantaged investments.

Practical Takeaway: Apply the 4.95 percent rate to your employment income, investment income, and self-employment income. Remember that retirement distributions and Social Security are exempt, and long-term capital gains face a 20 percent rate. Knowing which income types are taxed and at what rates helps you estimate your annual tax liability.

Income Deductions and Exemptions Available in Illinois

Illinois state tax law permits several deductions that reduce your taxable income before the 4.95 percent rate is applied. The standard deduction for 2024 provides a baseline reduction in taxable income for most taxpayers. For single filers, the standard deduction is $2,575. For married couples filing jointly, it is $5,150. For heads of household, it is $3,863. These amounts apply to residents of the state and reduce gross income to arrive at taxable income.

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Taxpayers may itemize deductions instead of taking the standard deduction if their itemized deductions exceed the standard deduction amount. Illinois allows deductions for state and local property taxes paid, state and local income taxes paid to other states, mortgage interest on primary residences, and charitable contributions to qualified organizations. However, the federal limit on state and local tax deductions (known as the SALT cap) of $10,000 annually also applies to Illinois state taxes.

Illinois provides a dependent exemption that reduces taxable income for each dependent claimed on your return. As of 2024, this exemption amounts to $2,575 per dependent. Dependents must meet the IRS definition, including being a U.S. citizen, national, or resident alien. This exemption can significantly reduce tax liability for families with multiple children or other eligible dependents.

Personal exemptions for the taxpayer and spouse are also available, each worth $2,575 for 2024. These exemptions are separate from the dependent exemptions and apply automatically to the taxpayer and spouse on a jointly filed return. Age-based exemptions provide additional deduction amounts for taxpayers age 65 and older, which is $1,000 of additional exemption per qualifying taxpayer.

Illinois also offers a Dependent Care Credit that reduces tax liability (rather than just reducing taxable income) for qualified expenses paid to care for dependents while the taxpayer works. The credit covers costs of day care, preschool, and similar services for children under age 13 and disabled dependents of any age. The credit amount depends on your income level and varies from 20 to 30 percent of qualifying expenses, up to $3,000 in expenses per dependent annually.

Practical Takeaway: Calculate whether your itemized deductions exceed the standard deduction for your filing status. Account for dependent exemptions and personal exemptions to determine your final taxable income. Consider whether you paid dependent care expenses, as the Dependent Care Credit can provide additional tax reduction.

Who Must File Illinois Income Tax Returns

Illinois requires most residents to file a state income tax return if their income exceeds certain thresholds. These thresholds vary based on filing status and age. For single filers under age 65, the filing requirement threshold for 2024 is approximately $3,500 in income from all sources. For married couples filing jointly where both are under age 65, the threshold is approximately $7,000. For heads of household, the threshold is approximately $4,550.

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Age affects filing requirements in Illinois. Taxpayers age 65 and older have higher thresholds. Single taxpayers age 65 and older must file if their income exceeds approximately $4,500. Married couples where at least one spouse is age 65 or older must file if their combined income exceeds approximately $8,000. These higher thresholds provide relief for older taxpayers with modest income.

Non-residents who earned income in Illinois during the tax year must file an Illinois tax return on that Illinois-source income, even if they did not live in the state. A non-resident working in Illinois is generally required to file if their Illinois income exceeds the filing threshold. Students who earned income in Illinois while attending school out of state may also need to file, depending on their income level.

Even if your income falls below the filing threshold, filing a return can be beneficial. Illinois has a Earned Income Credit (EIC) based on the federal Earned Income Tax Credit that provides refundable credits to low-income working individuals and families. If you have earned income and your household income is relatively low, filing allows you to claim this credit and potentially receive a refund even if no tax is owed.

Self-employed individuals generally must file a return if their net self-employment income is $400 or more, regardless of their total income. Self-employed individuals also owe self-employment tax to the federal