Illinois State Tax Return Form IL-1040: Schedules, Filing, and Deadlines

To file an Illinois state tax return on Form IL-1040, start from your completed federal Form 1040, carry your federal adjusted gross income to the IL-1040, apply Illinois subtractions, exemptions, and credits, and submit the return electronically through MyTax Illinois or by mail. Illinois uses a flat income tax rate of 4.95 percent of net income.1Illinois Department of Revenue. What’s New for 2025 The 2025 return is due April 15, 2026.2Illinois Department of Revenue. Due Date/Extension to File Income Tax Return

Do You Need to File an IL-1040

Full-year Illinois residents must file an IL-1040 any year they were required to file a federal return. The requirement applies even if your income was low enough that no Illinois tax would be owed. You may also need to file if your Illinois base income exceeds your personal exemption allowance, regardless of your federal filing status.3Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 5/502 – Returns and Notices

If you moved into or out of Illinois during the year, you file as a part-year resident and use Schedule NR to split your income by where you lived when you earned it.4Illinois Department of Revenue. Schedule NR IL-1040 Instructions Non-residents who earned wages, business income, or rental income from Illinois sources generally must file as well, unless withholding already covered the full Illinois liability.

One important boundary: Illinois has reciprocal agreements with Iowa, Kentucky, Michigan, and Wisconsin. If you live in one of those states and your only Illinois income was wages, you don’t owe Illinois tax on that compensation and don’t need to file, except to recover tax that was withheld in error.4Illinois Department of Revenue. Schedule NR IL-1040 Instructions

What to Gather Before You Start

The IL-1040 is built on top of your federal return, so finish federal Form 1040 first. From it you’ll pull your federal adjusted gross income (federal Line 11), which becomes the starting figure on the Illinois form. Also have ready:

  • Social Security numbers or ITINs for everyone on the return
  • W-2s and 1099s showing Illinois income and Illinois tax withheld
  • Property tax payment records and your property index number, if you’ll claim the property tax credit
  • Receipts for qualifying K-12 education expenses, if applicable

You can download a fillable PDF of Form IL-1040 from the Department of Revenue website or complete the return directly in MyTax Illinois without downloading anything.5Illinois Department of Revenue. 2025 IL-1040 Individual Income Tax Return The online portal does the math as you go.6Illinois Department of Revenue. File Form IL-1040, Individual Income Tax Return, on MyTax Illinois

Working Through the IL-1040

Your Illinois filing status generally matches whatever you used federally.7Illinois Department of Revenue. Filing Status – IL-1040, Individual Income Tax Return From federal AGI, the form walks you through additions, subtractions, your exemption allowance, and the 4.95 percent flat tax calculation.

The biggest subtraction for many Illinois filers sits on Line 5. Illinois does not tax Social Security benefits or qualifying retirement income, including pensions, 401(k) distributions, IRA withdrawals, government and military retirement plans, railroad retirement, self-employed retirement plans, and Roth IRA conversions.8Illinois Department of Revenue. Does Illinois Tax My Pension, Social Security, or Retirement Income? If any of that income flowed into your federal AGI, you subtract it here.

The personal exemption allowance for 2026 is $2,925 per exemption, with an extra $1,000 if you’re 65 or older or legally blind. The exemption disappears entirely if your federal AGI exceeds $500,000 on a joint return or $250,000 on any other return.9Illinois Department of Revenue. What Is the Illinois Personal Exemption Allowance?

Schedules You May Need to Attach

Schedule IL-WIT for Withholding

Schedule IL-WIT lists the Illinois income tax that was withheld from your pay and other income throughout the year, pulled from your W-2s and 1099s. The total feeds Line 25 of the IL-1040. If you claim any withholding credit on that line, you must attach Schedule IL-WIT along with copies of the W-2s and 1099s that back it up. Forgetting the attachment is one of the quickest ways to stall your refund, because the state has no way to verify what was withheld without it.10Illinois Department of Revenue. 2025 IL-1040 Schedule IL-WIT Instructions

Schedule M for Other Subtractions and Additions

Schedule M handles adjustments beyond the retirement subtraction. On the subtractions side, interest from U.S. Treasury bonds, savings bonds, and other federal obligations is exempt from Illinois tax if it was included in your federal AGI.11Illinois Department of Revenue. 2025 IL-1040 Schedule M Instructions You cannot subtract anything that isn’t on the Schedule M list. Items commonly assumed to be deductible but explicitly excluded include out-of-state income, unemployment compensation (except railroad unemployment), gambling losses, and federal itemized deductions.12Illinois Department of Revenue. IL-1040 Schedule M Instructions On the additions side, Schedule M captures income Illinois taxes that the federal government doesn’t, such as interest from other states’ municipal bonds. Totals flow to Lines 3 and 7 of the IL-1040.

Schedule NR for Part-Year Residents and Non-Residents

Schedule NR determines how much income Illinois can tax when you weren’t a full-year resident. Non-residents report only Illinois-source income. Part-year residents report everything earned while they lived in Illinois, plus any Illinois-source income earned while living elsewhere. Non-residents whose business income was earned partly inside and partly outside Illinois complete the Business or Farm Income Apportionment Worksheet. Temporary absences from Illinois during the year don’t convert you to a part-year resident.4Illinois Department of Revenue. Schedule NR IL-1040 Instructions

Schedule ICR for Credits

Schedule ICR is where homeowners, parents, and volunteer emergency workers claim credits that reduce the tax owed.13Illinois Department of Revenue. 2025 IL-1040 Schedule ICR Instructions The three most commonly claimed are:

  • Property tax credit of 5 percent of Illinois property taxes paid on your principal residence during the year, limited to the period you owned and lived there. Vacation homes and rental properties don’t qualify.
  • K-12 education expense credit of 25 percent of qualifying education expenses above $250, capped at $750 per family regardless of how many students qualify. The child must have been a full-time student under 21 at an Illinois school, and both parent and student must be Illinois residents.14Illinois Department of Revenue. Pub-112, Education Expense Credit General Rules
  • Volunteer Emergency Worker credit of $500 for volunteer firefighters and volunteer members of county or municipal emergency services agencies who served at least nine months and received no more than $5,000 in compensation. Emergency services volunteers must log at least 100 hours. A statewide $5 million cap applies, awarded first-come first-served.15Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 5/234

Illinois also offers an Earned Income Tax Credit and a Child Tax Credit on separate schedules, both tied to federal EIC eligibility. If you qualified for the federal credit, check whether you also qualify at the state level.

Submitting the Return

The simplest route is MyTax Illinois at mytax.illinois.gov. You can file with or without a MyTax account.6Illinois Department of Revenue. File Form IL-1040, Individual Income Tax Return, on MyTax Illinois Commercial tax software also supports Illinois e-filing. Electronic returns process faster, and refunds arrive weeks sooner than with paper returns.

If you file on paper, the mailing address depends on whether you’re sending a payment:16Illinois Department of Revenue. 2025 IL-1040 Instructions

  • 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

Using the wrong box slows processing, so confirm which one applies before you mail.

Deadline and Extension

The 2025 IL-1040 is due April 15, 2026.2Illinois Department of Revenue. Due Date/Extension to File Income Tax Return Illinois grants an automatic six-month filing extension to October 15, 2026, with no separate form required if all you need is more time to file.

The extension covers filing, not paying. Any tax owed must still be paid by April 15 to avoid penalties and interest. If you know you’ll owe but aren’t ready to file, submit Form IL-505-I with your payment by the original deadline.

If You Cannot Pay in Full

If the balance due is more than you can pay at once, the Department of Revenue offers installment plans. All your tax returns must be filed and current before you can apply.17Illinois Department of Revenue. Payment Plan Information You can request a plan through MyTax Illinois, where a pre-approved option may be available immediately, or propose custom terms that a collections agent will review. Paper applicants submit Form CPP-1.

If the total balance including penalties and interest exceeds $15,000, you’ll need to submit detailed financial information on Form EG-13-I. Your monthly payment and plan length depend on what the financial disclosure shows. Interest keeps accruing while you’re on the plan, so paying faster when you can lowers the total cost.