Illinois State Tax Forms (2026 & 2027 Guide)

Illinois uses a relatively simple state tax system with a flat income tax rate, but there are still specific forms required depending on your residency status, income, and credits.

The primary form most taxpayers will use is the IL-1040.

Main Illinois Tax Forms

Illinois has different primary forms based on residency.

• IL-1040 → Resident Income Tax Return
• Schedule NR → Nonresident and Part-Year Resident Computation

These forms are used to report income, calculate tax, and determine how much income is taxable in Illinois.

Common Illinois Supporting Forms

Depending on your financial situation, you may need additional schedules.

• Schedule M → Additions and subtractions to income
• Schedule CR → Credit for taxes paid to another state
• Schedule IL-E/EIC → Illinois Earned Income Credit
• Schedule 1299-C → Income tax credits

These schedules help apply state-specific adjustments and credits.

Forms for Property Tax and Credits

Illinois offers certain credits and benefits that require additional forms.

• Schedule ICR → Illinois Property Tax Credit
• Schedule RUT-50 → Vehicle use tax (for certain purchases)
• Schedule RUT-25 → Title and registration tax

These forms can help reduce your tax liability or report specific transactions.

Forms for Special Situations

Illinois provides additional forms for specific tax needs.

• IL-1040-ES → Estimated tax payments
• IL-505-I → Extension of time to file
• IL-1040-X → Amended return

These are used if you need more time, owe estimated taxes, or need to correct a return.

How Illinois Taxes Income

Illinois uses a flat income tax rate.

• All taxable income → 4.95%

Example: If your taxable income is $65,000, your Illinois state tax would be $3,217.50 regardless of filing status.

Deductions and Special Rules

Illinois has different tax rules compared to federal law.

• No federal-style standard deduction
• Personal exemption allowance is available
• Certain retirement income is not taxed

These differences can affect your taxable income.

Who Needs to File

You generally need to file an Illinois return if you:

• Are a resident with taxable income
• Earn income from Illinois as a nonresident
• Have Illinois tax withheld and want a refund

Part-year residents must report income earned while living in the state.

Electronic Filing Recommendation 💻

• Use tax software to automatically generate IL-1040 and required schedules
• Review state-specific adjustments carefully
• Include all necessary credit forms
• E-file for faster refunds and fewer errors

Summary

Illinois state taxes are filed using Form IL-1040, along with supporting schedules for adjustments, credits, and special situations.

Because Illinois uses a flat tax rate and has its own rules for exemptions and deductions, understanding the correct forms can help ensure accurate filing and potentially lower your tax bill.