Illinois Tax Calculator
Illinois applies a single flat rate to all taxable income, a structure required by the state constitution. What sets Illinois apart is its treatment of retirement income: Social Security, pensions, and withdrawals from 401(k) and IRA accounts are all fully excluded from state tax, regardless of how much you receive. This calculator applies the flat rate to your entered wage or salary income.
State Tax
$4,950Effective Rate
4.95%Marginal Rate
4.95%| Rate | Bracket Range | Tax |
|---|---|---|
| 4.95% | $0+ | $4,950 |
| Total | $4,950 | |
How Illinois income tax works
- Illinois multiplies your taxable income by one flat rate required by the state constitution.
- Retirement income of every kind — Social Security, pensions, and 401(k)/IRA withdrawals — is excluded from state tax entirely.
- The calculator applies the current flat rate to your entered income for an instant result.
Need the exact bracket thresholds instead of an estimate? See the Illinois tax brackets for 2026 .
Estimate your Illinois property tax by county, compare every state at the state tax brackets hub , or see the full tax-by-state directory .
Frequently asked questions
How is Illinois income tax calculated?
Illinois applies a single flat rate to your taxable income, with no brackets involved. The calculator multiplies your entered income by that rate to show your exact state tax.
Does Illinois tax Social Security or retirement income?
No. Illinois fully excludes Social Security, pension income, and 401(k)/IRA withdrawals from state taxable income, no matter the amount.
Why does Illinois use a flat rate?
The Illinois Constitution requires a single flat income tax rate, so every taxpayer pays the same percentage of their taxable income regardless of how much they earn.
How much state tax will I pay in Illinois?
Since Illinois uses a flat rate, your state tax is that rate applied to your taxable wage income. Enter your figures above for an instant total.
Sources
Related insights
Use these guides for rule explanations, planning context, and follow-up questions beyond the calculator result.
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