How this calculator works
Tax year: 2024. Illinois applies 4.95% after allowed subtractions and $2,775 exemptions for yourself, a joint spouse and eligible dependents. Exemptions are unavailable above $250,000 federal AGI, or $500,000 jointly; this worksheet assumes the entered state AGI equals federal AGI for that test. Federal income tax, Social Security, Medicare, state disability insurance and unentered credits are excluded. The remaining amount is not full take-home pay. Rate-band estimates can differ from the official small-income tax tables. Property tax, where shown, is separate from the pay-period amount.
Formula
Taxable income = max(0, state AGI - additional eligible adjustments - allowed deductions and exemptions). Apply state bands and applicable supplements, then subtract supplied non-refundable credits. Average period amount = (AGI - listed income taxes - post-tax deductions) / annual pay periods.
Worked example
A single filer with $12,775 AGI, no dependents or other adjustments, and one $2,775 exemption has $10,000 taxable income and $495 state tax.
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Frequently asked questions
Which year does this use?
The fixed state rules on this page are for 2024. Later-year returns require updated thresholds and deductions.
Is the remaining amount my paycheque?
No. Federal tax, payroll contributions and other unentered deductions are not included. It is income after only the listed worksheet items.
Should retirement contributions be entered twice?
No. Enter them only if they are eligible state adjustments not already excluded from the AGI you supplied.