Estimate your Illinois state income tax plus combined federal and IL state tax for 2026. 4.95% flat rate.
Illinois has a constitutionally mandated flat income tax rate of 4.95% on all taxable income. Illinois cannot implement a graduated income tax without a constitutional amendment. Illinois residents often face high property taxes alongside the flat income tax. Use the calculator above to estimate your combined federal and Illinois state income tax for 2026. State tax figures use a simplified rate — for precise Illinois state tax calculations, consult the Illinois Department of Revenue or a licensed tax professional.
Illinois uses a 4.95% flat rate state income tax structure. Like most states, Illinois starts its calculation from your federal Adjusted Gross Income (AGI), then applies state-specific adjustments — subtracting income Illinois excludes from taxation (such as certain pension or Social Security income) and adding back any income Illinois taxes that the federal government does not. After adjustments, the Illinois standard deduction is applied, then the 4.95% flat rate is applied to arrive at state taxable income.
Illinois income tax is collected through employer paycheck withholding for W-2 employees and through quarterly estimated payments for self-employed residents and those with significant non-wage income. The Illinois state return is generally due April 15, aligned with federal returns. Part-year residents and nonresidents who earn income sourced in Illinois must also file a Illinois return for that income portion.
Your Illinois state income taxes are deductible on your federal Schedule A as part of the SALT (State and Local Tax) deduction, capped at $40,400 in 2026 under OBBBA. At the 22% federal bracket, paying $2,932 in Illinois state income tax generates approximately $645 in federal tax savings, reducing the true net cost of your Illinois taxes to about $2,287 for itemizing taxpayers.
Jordan is a single filer earning $75,000 in Illinois. This shows how federal and Illinois state income tax are calculated together.
Moving to a no-income-tax state (Texas, Florida, Nevada, or Wyoming) would save Jordan approximately $2,932/year ($244/month) in state income taxes. However, no-income-tax states often fund services through higher property taxes, sales taxes, or other fees, so a complete comparison requires evaluating all taxes together, not just income tax.
Illinois Tax Rate and Annual Filing
Illinois residents earning above the state filing threshold must file a Illinois income tax return annually, typically due April 15. The 4.95% flat rate applies after Illinois-specific deductions and any state tax credits. Employers withhold Illinois state income tax from employee paychecks throughout the year using Illinois withholding tables, and any balance owed or refund due is settled when the annual state return is filed. Self-employed Illinois residents make quarterly estimated payments to the state in addition to their federal quarterly estimated tax payments.
Federal SALT Deduction Reduces Net State Tax Cost
State income taxes paid in Illinois reduce your federal taxable income through the SALT deduction (capped at $40,400 in 2026 under OBBBA). For a Illinois resident in the 22% federal bracket paying $2,932 in state income tax, the SALT deduction recovers approximately $645 in federal taxes, so the true after-federal-benefit cost of Illinois state income tax is about $2,287. This offset only benefits taxpayers who itemize deductions on federal Schedule A rather than taking the standard deduction.
Total Tax Burden: State Income Tax Is One Piece
State income tax is one component of your total tax burden in Illinois. Property taxes, local income taxes (in some Illinois cities and counties), and state and local sales taxes also contribute to your overall cost of living. When comparing Illinois to other states, evaluate all tax types together rather than income tax in isolation. Use the calculator above to see your combined federal and Illinois state effective rate at your specific income level.
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Illinois has a 4.95% flat rate state income tax for 2026. Illinois has a constitutionally mandated flat income tax rate of 4.95% on all taxable income. Illinois cannot implement a graduated income tax without a constitutional amendment. Illinois residents often face high property taxes alongside the flat income tax. The state income tax is calculated separately from federal income tax and is paid through payroll withholding or quarterly estimated payments.
Illinois has its own state standard deduction separate from the federal standard deduction ($15,750 single, $31,500 MFJ in 2026). For precise Illinois state deduction amounts, consult the Illinois Department of Revenue or a state tax professional.
Illinois's 4.95% flat rate state income tax can be compared to other states using our state tax calculator above. The U.S. average top marginal state income tax rate is approximately 5-6%. Nine states have no income tax at all (Alaska, Florida, Nevada, New Hampshire, South Dakota, Tennessee, Texas, Washington, Wyoming), while California has the highest at 13.3%.
Illinois offers state tax credits and deductions that may reduce your state tax liability. Common state credits include earned income credits, child tax credits, and credits for the elderly. Consult the Illinois Department of Revenue website or a licensed tax professional for credits specific to your situation and income level.
Use the calculator above. Enter your income and IL is pre-selected as your state. The calculator computes your 2026 federal income tax using the One Big Beautiful Bill Act brackets (10%-37%), adds your estimated Illinois state income tax (4.95% flat rate simplified), and displays your total tax burden, combined effective rate, and annual take-home pay. All calculations happen instantly in your browser.