Illinois Paycheck Calculator
Calculate your take-home pay after federal, Illinois state (flat 4.95%), Social Security, and Medicare. Illinois uses a unique per-period allowance system — no annualization needed.
Illinois Paycheck Calculator
2025 tax year · estimate
How Illinois taxes your paycheck
Illinois uses a flat 4.95% income tax rate with a unique per-period allowance deduction. Unlike most states, IL doesn't annualize wages for withholding.
- Start with your gross pay per period
- Subtract pre-tax deductions (401k, health insurance, HSA)
- Calculate per-period allowance: (IL-W-4 allowances × $2,850) ÷ pay periods
- Subtract per-period allowance from adjusted gross pay
- Multiply remaining taxable wages by 4.95%
Formula: Tax = [Gross Pay − Pre-Tax − (Allowances × $2,850 ÷ Pay Periods)] × 4.95%
Illinois tax rate (2025)
Per allowance: $2,850/year ($109.62/biweekly period)
Filing status: Not used — allowances only
No standard deduction
IL-W-4 allowance values per pay period
| Pay Frequency | Periods | Per Allowance |
|---|---|---|
| Weekly | 52 | $54.81 |
| Biweekly | 26 | $109.62 |
| Semi-monthly | 24 | $118.75 |
| Monthly | 12 | $237.50 |
Who uses this calculator
Illinois employees
Verify your paycheck's 4.95% state withholding with per-period allowance deductions.
Chicago workers
No city income tax in Chicago. Your take-home is federal + IL state + FICA only.
Reciprocal state workers
IL has reciprocity with WI, MI, IA, and KY. If you live in one of these states, you may be exempt from IL withholding.
Retirees
Retirement income, Social Security, and pension income are exempt from Illinois income tax.
Job seekers
Illinois's flat 4.95% is predictable. No surprises from progressive brackets.
Payroll administrators
Verify the unique per-period formula: (allowances × $2,850) ÷ pay periods.
Frequently asked questions
How is Illinois state income tax calculated?
Illinois uses a flat 4.95% income tax rate. The unique feature is the per-period allowance formula: (IL-W-4 allowances × $2,850) ÷ pay periods. This per-period deduction is subtracted from gross pay before applying the 4.95% rate. No annualization is needed.
How do IL-W-4 allowances work?
Each Line 1 allowance on your IL-W-4 provides $2,850 in annual tax-free income. This is divided by your number of pay periods to create a per-period allowance. For biweekly (26 periods), each allowance shields about $109.62 per paycheck.
Does Illinois have a standard deduction?
No. Illinois does not use a standard deduction. Instead, it uses the personal exemption allowance system on the IL-W-4 form.
Does Illinois have local income taxes?
No. Illinois does not permit local income taxes on wages. Only state and federal taxes apply to your paycheck.
Is 401(k) pre-tax for Illinois state tax?
Yes. 401(k), 403(b), and Section 125 (health insurance/FSA) contributions are all pre-tax for Illinois state income tax.
What income is exempt from Illinois tax?
Retirement/pension income, Social Security benefits, and military pay are all exempt from Illinois income tax. Wages and salaries are fully taxable at 4.95%.
How accurate is this calculator?
This calculator provides a close estimate based on 2025 Illinois tax rates and the per-period allowance formula. Your actual paycheck may vary based on your employer's payroll system and IL-W-4 elections.