Last updated: December 17th, 2025
Each state has unique income tax withholding rules. Below are Illinois's 2026 withholding instructions, including allowance calculations, standard deduction adjustments, and the percentage method for determining tax due.
Employers must also adhere to federal income tax withholding rules. More information can be found here about federal rates.
Alternatively, employers can automatically calculate payroll withholding by using ezPaycheck.
| State Abbreviation | IL |
|---|---|
| State Tax Withholding State Code | 17 |
| Acceptable Exemption Form | None |
| Basis For Withholding | State Exemptions |
| Acceptable Exemption Data | Number of Exemptions / Number of Additional Exemptions |
| TSP Deferred | No |
| Special Coding | None |
| Additional Information | None |
| Official State Tax Website | Visit Official Website |
Illinois allows 1 withholding allowance for yourself (if no one else can claim you) and 1 for your spouse if you will claim your spouse as a dependent on your IL-1040 (spouse has no income). You may claim 1 for each eligible dependent. Illinois also permits additional allowances for age and blindness: if you or your spouse is 65 or older, or legally blind, each such condition is an extra allowance (each box checked in the IL-W-4 worksheet adds one). Moreover, IL's worksheet converts excess itemized deductions into allowances: any amount of deductions exceeding the standard deduction, divided by $1,000, yields additional allowances.
| Component | Allowances | Notes |
|---|---|---|
| Yourself | 1 allowance | If no one else can claim you |
| Spouse | 1 allowance | If spouse has no income and will be claimed as dependent |
| Each Dependent | 1 allowance | Per eligible dependent |
| Age 65+ (Employee or Spouse) | 1 allowance each | Per person who is 65 or older |
| Blind (Employee or Spouse) | 1 allowance each | Per person who is legally blind |
| Itemized Deductions | Calculated allowances | (Excess deductions ÷ $1,000) = additional allowances |
Total Allowances = Basic (Yourself + Spouse + Dependents) + Age/Blind Allowances + (Excess Itemized Deductions ÷ $1,000)
An elderly or blind taxpayer and spouse could claim up to four total allowances for age/blindness if both qualify. Itemized deductions exceeding the standard deduction can also add allowances.
For links to official state tax and revenue websites for all 50 states, visit our State and Local Tax Sites page.
Subtract the biweekly Thrift Savings Plan contribution from the gross biweekly wages.
Multiply the adjusted gross biweekly wages times 26 to obtain the annual wages.
Determine the exemption allowance by applying the following guideline and subtract this amount from the annual wages.
Exemption Allowance = $2,925 × Number of Exemptions
Determine the additional allowance by applying the following guideline and subtract this amount from step 3 to compute the taxable income.
Additional Allowance = $1,000 × Number of Additional Exemptions
Multiply the taxable income computed in step 4 times 4.95 percent to determine the amount of Illinois tax withholding.
Annual Tax = Taxable Income × 4.95%
Divide the annual Illinois tax withholding by 26 to obtain the biweekly Illinois tax withholding.
Want to calculate in an easier way? Learn how to calculate Illinois taxes via ezPaycheck below.
Learn More| Withholding Allowance | Annual Amount |
|---|---|
| 1 | $2,925 |
Formula: $2,925 × Number of Exemptions
Standard exemption allowance.
Rate: 4.95%
Illinois uses a flat tax rate of 4.95% on taxable income after exemptions.
ezPaycheck simplifies payroll calculations, including Illinois's withholding rules. Easily compute taxes, generate reports, and print paychecks or tax forms.
We strive to provide accurate and up-to-date Illinois state tax information for 2026. If you notice any discrepancies, errors, or have questions about the tax rates or calculations shown on this page, please contact our support team. We appreciate your feedback and will review and update the information as needed.
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