Illinois Tax Calculator
Calculate your Illinois state income tax liability. Illinois has a flat 4.95% income tax rate with additional local taxes in some areas.
Tax Summary
Tax Breakdown
Illinois Tax Information
Understanding Illinois State Income Tax
Illinois has a flat state income tax rate of 4.95%, making it one of the higher-tax states in the U.S. Some counties add additional local taxes, with Cook County having the highest local rate.
Illinois Tax Rates
| Tax Type | Rate | Notes |
|---|---|---|
| State Income Tax | 4.95% | Flat rate on taxable income |
| Cook County Tax | 1.31% | Highest local rate |
| Collar Counties | 0.99% | DuPage, Lake, McHenry, Kane, Will |
Taxable Income Calculation
Illinois taxable income starts with federal AGI and makes adjustments for Illinois-specific deductions and credits.
Illinois Taxable Income Formula
Federal AGI - Illinois Additions + Illinois Subtractions - Illinois Deductions
- Additions: Income taxed federally but not in Illinois
- Subtractions: Income taxed in Illinois but not federally
- Deductions: Standard or itemized deductions
Illinois Tax Credits
Major Tax Credits
- Earned Income Credit: For low-income workers
- Education Savings Credit: For college savings
- Property Tax Credit: Renters and homeowners
- Child Care Credit: For childcare expenses
Special Credits
- Research Credit: For R&D expenses
- Alternative Energy Credit: For renewable energy
- Historic Preservation Credit: For restoration
- Employer Child Care Credit: For business childcare
Local County Taxes
Several Illinois counties impose additional income taxes. Cook County has the highest rate, while the collar counties have a uniform rate.
| County | Tax Rate | Combined Rate |
|---|---|---|
| Cook County | 1.31% | 6.26% |
| DuPage County | 0.99% | 5.94% |
| Lake County | 0.99% | 5.94% |
| McHenry County | 0.99% | 5.94% |
| Kane County | 0.99% | 5.94% |
| Will County | 0.99% | 5.94% |
Illinois vs. Other States
| State | Top Rate | Local Max | Combined Max |
|---|---|---|---|
| Illinois | 4.95% | 1.31% | 6.26% |
| California | 13.3% | 2.5% | 15.8% |
| New York | 10.9% | 4.875% | 15.775% |
| Texas | 0% | 0% | 0% |
Filing Requirements
Who Must File
- Illinois residents with income
- Part-year residents
- Income over filing threshold
- Required by federal filing
Filing Thresholds
- Single under 65: No minimum
- Married under 65: No minimum
- Head of Household: No minimum
- Illinois requires filing if federal filing required
Key Takeaways
- Illinois has a flat 4.95% state income tax rate
- Cook County adds 1.31% for a combined 6.26% rate
- Collar counties add 0.99% for a combined 5.94% rate
- Taxable income based on federal AGI with adjustments
- Various tax credits available for education, childcare, and more
- Illinois ranks high in overall tax burden
- Consult Illinois Department of Revenue for specific requirements