Illinois tax forms start with Form IL-1040, the individual income tax return every resident filer uses, and branch out into schedules for specific credits or nonresident income and into separate returns for corporations, partnerships, S-corporations, and employers. Which forms you need depends on who you are, where you lived, and what credits you plan to claim. The sections below walk through each form, what it does, and when it attaches to your return.
Form IL-1040: The Individual Income Tax Return
Form IL-1040 is the main return Illinois residents file each year. It begins with your federal adjusted gross income, taken from line 11 of your federal Form 1040 or 1040-SR, then applies Illinois-specific additions and subtractions.1Internal Revenue Service. Adjusted Gross Income Common subtractions include federally taxed Social Security benefits and interest on U.S. government bonds, neither of which Illinois taxes.2Illinois Department of Revenue. Pub-101, Income Exempt from Tax
After adjustments, you subtract the personal exemption allowance. For tax year 2026, each exemption is worth $2,925, and the allowance phases out entirely if federal adjusted gross income exceeds $500,000 on a joint return or $250,000 for any other filing status.3Illinois Department of Revenue. What Is the Illinois Personal Exemption Allowance? What remains is taxed at the flat 4.95 percent rate.4Illinois Department of Revenue. Income Tax Rates Because the state return builds on the federal one, IDOR requires you to attach your federal return and schedules when you submit the IL-1040.5Illinois Department of Revenue. 2025 Form IL-1040 Instructions
The IL-1040 also includes a line (Line 21) for use tax owed on untaxed out-of-state or online purchases. You have to enter something on that line, even if the amount is zero.5Illinois Department of Revenue. 2025 Form IL-1040 Instructions If your use tax liability runs over $600 ($1,200 for married filing jointly), you cannot report it on the IL-1040 and must file Form ST-44 instead.6Illinois Department of Revenue. Use Tax for Individuals – Questions and Answers
Individual Schedules That Attach to the IL-1040
Several supplemental schedules pair with the IL-1040 depending on your situation. Credits and exemptions claimed without the correct schedule will not be applied.
Schedule NR for Part-Year Residents and Nonresidents
If you lived in Illinois for only part of the year, or earned income from Illinois sources while living in another state, file Schedule NR with your IL-1040. It determines what portion of your total income Illinois can tax and calculates the tax on that portion.7Illinois Department of Revenue. IL-1040 Schedule NR Instructions
Schedule ICR for Property Tax, Education, and Volunteer Credits
Schedule ICR is where you calculate three nonrefundable credits: the property tax credit, the K-12 education expense credit, and the Volunteer Emergency Worker credit. The property tax credit equals 5 percent of qualifying property taxes paid on your principal residence, and you will need your property index number from your tax bill to complete the schedule.8Illinois Department of Revenue. 2025 IL-1040 Schedule ICR Instructions For the education credit, keep receipts for qualifying tuition and book fees.
Schedule IL-E/EITC for Exemptions and Earned Income Credit
Schedule IL-E/EITC does double duty. It calculates your dependent exemption allowance and figures the Illinois Earned Income Tax Credit and Child Tax Credit. The Illinois EITC is refundable, so it can produce a refund even if you owe no state tax. Since 2023, Illinois has expanded EITC eligibility beyond the federal rules, meaning some filers who do not qualify federally may still qualify at the state level.9Illinois Department of Revenue. 2025 Schedule IL-E/EITC Instructions
Form IL-1040-ES for Estimated Payments
If you expect to owe more than $1,000 in state tax after withholding and credits, Illinois requires quarterly estimated payments on Form IL-1040-ES. This typically applies to freelance earnings, rental income, and investment gains that are not subject to withholding.10Illinois Department of Revenue. Estimated Income Tax Payments for Individuals
Business and Employer Forms
Businesses operating in Illinois use entirely separate returns with their own rates and schedules.
Form IL-1120 for Corporations
Corporations file Form IL-1120, which reports both income tax and personal property replacement tax. The combined rate is 9.5 percent: 7 percent income tax plus 2.5 percent replacement tax on corporate net income.11Illinois Department of Revenue. What Is the Tax Rate for Businesses, Trusts, and Estates? The return uses the entity’s Federal Employer Identification Number rather than a Social Security number.12Illinois Department of Revenue. IL-1120 Instructions
Form IL-1065 for Partnerships and S-Corporations
Partnerships and S-corporations file Form IL-1065 for replacement tax, which runs at a lower 1.5 percent rate. These entities also issue Schedule K-1-P to each partner or shareholder, reporting that person’s share of Illinois income.13Illinois Department of Revenue. 2025 IL-1065 Instructions Partnerships and S-corporations may also elect to pay a 4.95 percent pass-through entity tax on behalf of their owners, who can then claim it as a credit on their individual returns.11Illinois Department of Revenue. What Is the Tax Rate for Businesses, Trusts, and Estates?
Form IL-941 for Employers
Any employer withholding Illinois income tax from employee paychecks files Form IL-941 quarterly. The form reports total withholding for the quarter, and all IL-941 returns must be filed electronically.14Illinois Department of Revenue. Publication 131, Withholding Income Tax Payment and Filing Requirements
Form IL-1040-X for Amending a Return
If you discover an error on a return you already filed, use Form IL-1040-X to correct it. For mistakes that originated on the state return, you generally have until the latest of three years after the extended due date, three years after you filed the original, or one year after the tax was paid.15Illinois Department of Revenue. Amending My Return
If the change stems from a federal adjustment, the window is different: two years plus 120 days after the federal change is finalized. Missing the deadline forfeits any refund you would otherwise receive.15Illinois Department of Revenue. Amending My Return
Where to Get the Forms and How to File
Every form above is available in fillable PDF on the Illinois Department of Revenue website. Individual filers can also submit the IL-1040 electronically through MyTax Illinois at no charge, and e-filing generally produces faster refunds.16Illinois Department of Revenue. File Form IL-1040, Individual Income Tax Return, on MyTax Illinois Third-party tax software supports Illinois e-filing as well if you prepare your federal and state returns together.
If you file a paper IL-1040, the mailing address depends on whether a payment is enclosed:
- No payment enclosed: Illinois Department of Revenue, PO Box 19041, Springfield, IL 62794-9041
- Payment enclosed: Illinois Department of Revenue, PO Box 19027, Springfield, IL 62794-9027
MyTax Illinois accepts electronic payments directly from a checking or savings account. Credit card payments are also accepted, though the processor charges a convenience fee.17Illinois Department of Revenue. Make a Payment – Options for Individuals
Before You Gather the Forms
You need a completed federal return in hand before you can start the IL-1040, because your federal adjusted gross income is the first number on the state form. Also gather your W-2s, any 1099s for interest, dividends, freelance income, or retirement distributions, and Social Security numbers or ITINs for everyone on the return. Missing or incorrect identification numbers can delay processing or cause a rejection. If you plan to claim the property tax credit, pull your property tax bill with the property index number. For the K-12 education credit, keep receipts for qualifying tuition and book fees.
The Deadline
Form IL-1040 for tax year 2025 is due April 15, 2026, and any tax owed is due the same day. Illinois automatically grants a six-month filing extension to October 15, 2026, with no paperwork required, but the extension covers filing only. Payment is still due April 15 to avoid penalties and interest.18Illinois.gov. Illinois Department of Revenue Urges Taxpayers to Act Now Ahead of April 15 Filing Deadline If you need more time beyond the automatic extension, Illinois will match a federal extension; attach a copy of the IRS approval to your state return.19Illinois Department of Revenue. Automatic Extension Payment for Individuals Filing Form IL-1040