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Illinois Income Tax 2026: Flat 4.95% Rate, Deductions & Free Calculator

October 17, 2026 · 5 min read · By the DollarWise team
Illinois Income Tax 2026: Flat 4.95% Rate, Deductions & Free Calculator
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Illinois keeps its income tax refreshingly simple: one flat rate, no brackets, no bracket math. For 2026, that rate is 4.95% on your net income — confirmed by current 2026 guides from NerdWallet and the Tax Foundation. Whether you earn $30,000 or $300,000, the same percentage applies to every taxable dollar.

That simplicity hides a few quirks worth knowing — generous retirement-income exemptions, a property tax credit, and a state EITC that can put money back in your pocket. This guide covers the 2026 rate, the deductions and credits that matter most, and how to get an exact estimate in seconds with our free Illinois income tax calculator.

The 2026 Illinois rate: flat 4.95%

Illinois does not have tax brackets. Your Illinois income tax is simply:

Illinois net income x 4.95%

Net income starts with your federal adjusted gross income (AGI), then Illinois applies its own additions and subtractions. The big subtractions are what make Illinois friendlier than the flat rate suggests: Social Security benefits, most pension income, and 401(k)/IRA distributions are exempt from Illinois tax entirely.

Deductions and credits that lower your bill

Illinois EITC. Illinois matches 20% of your federal Earned Income Tax Credit, and it’s refundable — it can produce a refund even if you owe no tax. For 2026, the state credit ranges from $130 to $1,609.

Property tax credit. Homeowners can claim a credit equal to 5% of Illinois property tax paid on their principal residence — real money in a state with some of the country’s highest property taxes (effective rate around 1.88%).

Education expense credit. Parents paying tuition or fees for K-12 students at Illinois schools can claim a credit for qualifying expenses above $250.

Retirement income subtraction. As noted above, federally taxed retirement income — Social Security, pensions, IRA and 401(k) distributions — is subtracted from Illinois income. This is why Illinois is a popular retirement state despite high property taxes.

A quick calculation example

Say your federal AGI is $80,000, you received $10,000 in pension income, and you paid $6,000 in Illinois property tax on your home:

  1. Start: $80,000 AGI
  2. Subtract pension income: $80,000 - $10,000 = $70,000 net income
  3. Apply the flat rate: $70,000 x 4.95% = $3,465
  4. Subtract property tax credit: $3,465 - ($6,000 x 5%) = $3,465 - $300 = $3,165

Your actual return may include other modifications and credits — but this shows how the flat rate and the subtractions interact.

Who has to file in Illinois?

You generally must file an Illinois return (Form IL-1040) if you were required to file a federal return, or if you want to claim a refund or credits like the EITC. Part-year residents and nonresidents with Illinois-source income file too, with income apportioned to Illinois.

The deadline for 2026 tax-year returns is April 15, 2027. Illinois grants an automatic six-month filing extension to October 15, but — as with the feds — the tax itself must be paid by April 15 to avoid interest and penalties.

How Illinois compares to its neighbors

Illinois’s flat 4.95% looks different next to its neighbors’ systems:

Indiana charges a flat 2.95% state rate plus county taxes — a combined rate that often lands just under Illinois’s 4.95%.

Wisconsin uses graduated brackets topping out at 7.65% — higher earners pay noticeably more than in Illinois.

Iowa moved to a flat 3.8% rate — lower than Illinois across the board.

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Missouri has graduated brackets up to 4.7% — roughly comparable for middle earners, slightly lower at the top.

Kentucky charges a flat 4% — lower than Illinois for everyone.

The flat-rate structure is Illinois’s selling point for high earners (no 7%+ top bracket like some neighbors), while the retirement-income exemptions make it friendlier to retirees than the headline rate suggests. The real Illinois tax pain is property tax, not income tax.

Illinois tax deadlines and penalties

April 15 is the magic date: returns due, payment due. The automatic six-month extension covers filing only — not payment.

Underpayment interest accrues on tax paid after April 15, even with an extension. If you owe, pay your best estimate by the deadline and true it up later.

Estimated payments are required if you’ll owe $1,000 or more beyond withholding — common for freelancers and landlords. Illinois follows the federal quarterly schedule.

Late filing penalties start at 2% of unpaid tax per month. Illinois is not a state to ignore and hope for the best.

Retirement in Illinois: the full picture

Illinois is genuinely tax-friendly for retirees on the income side: no tax on Social Security, pensions, or 401(k)/IRA distributions, plus the flat 4.95% on any other income. The catch is property tax — among the highest effective rates in the nation at around 1.88%. Retirees weighing Illinois should run both numbers: the income-tax savings are real, but they can be outweighed by property tax on a valuable home. The senior freeze and homestead exemptions help — check whether you qualify.

Frequently asked questions

What is the Illinois income tax rate for 2026?

A flat 4.95% on net income — no brackets. Confirmed by 2026 sources including NerdWallet and the Tax Foundation.

Does Illinois tax Social Security benefits?

No. Illinois exempts Social Security benefits, and most other retirement income (pensions, 401(k)/IRA distributions) is also exempt at the state level.

How do I calculate my Illinois income tax?

Take federal AGI, apply Illinois additions and subtractions (like the retirement-income subtraction), multiply the result by 4.95%, then subtract credits. Our free calculator at /tools/illinois-income-tax-calculator/ does it in seconds.

When are Illinois taxes due in 2026?

Returns for tax year 2026 are due April 15, 2027. Filing can be extended to October 15, but payment is still due April 15.

#tax#illinois#income tax
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Written by the DollarWise team

We turn confusing money topics into plain-English guides for beginners. Every article is written to be actionable on day one — no jargon, no hype, no sales pitch.

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