How to file an Illinois state tax return

This article was fact-checked by our editors and Jennifer Samuel, senior product specialist for Credit Karma. It has been updated for the 2019 tax year.

Illinois’ license plate motto — “The Land of Lincoln” — may imply that residents live a simple life, but the state has complicated tax laws, even though it has a flat income tax rate.

Like many states, Illinois has more than one state-level tax, including sales tax, a gas tax, gaming tax and hotel tax. Unlike the progressive federal income tax system, Illinois has a flat individual income tax.

This guide will focus on things to know about Illinois’ individual income tax.

• The basics of Illinois state tax
• Illinois deductions and credits to know
• How to file your Illinois state tax return
• If you owe and can’t pay
• Tracking your Illinois state tax refund

The basics of Illinois state tax

Taxing body

The Illinois Department of Revenue, or IDOR, administers tax laws and collects state tax revenue.

You can get general tax information by calling 1-800-732-8866 or 1-217-782-3336. Calls are answered Monday through Friday from 8 a.m. to 5 p.m. The TDD number is 1-800-544-5304.

You can also get help at IDOR’s local offices in Chicago, Des Plaines, Fairview Heights, Marion, Rockford and Springfield. You don’t need an appointment, but if your question is complicated, call ahead so someone will be ready to assist you.

Filing and payment deadline

For 2019 state taxes, the state has extended the filing and payment deadline. Illinois residents now have until July 15, 2020 to file their state returns and pay any state tax they owe for the year. As with the federal deadline extension, Illinois won’t charge interest on unpaid balances between April 15 and July 15, 2020.

You don’t need to do anything to get this extension. It’s automatic for all Illinois taxpayers. But keep in mind that if you’re expecting a refund, you might want to go ahead and file as soon as possible. During the coronavirus crisis, the state is continuing to process tax returns and issue refunds.

Illinois state tax returns and any tax you owe are due April 15, the same day that your federal return is due. But if that day falls on a weekend or holiday, the deadline will be the next business day.

State residents can get a six-month filing extension. If you get a longer extension to file your federal return though, the state will automatically match it.

But keep in mind: If you owe tax, you must file Form IL-505-I, Automatic Extension Payment for Individuals, and pay what you owe by the original tax-filing deadline to avoid paying penalties and interest charges.

Filing statuses

Most Illinois taxpayers should use the same state filing status as they use on their federal return. There are two exceptions that both apply if you used married filing jointly as your status on your federal return.

• If you’re an “injured spouse” (i.e., your spouse individually owes money to a government agency), you should file as married filing separately. If you file jointly and are expecting a refund, the state can take that refund to pay your spouse’s tax liability.
• If you’re married and either you or your spouse is not living in Illinois full time (for example, if one of you serves in the military), you can choose to file as married filing separately. If you file jointly, both you and your spouse will be treated as residents.

If you’re in a civil union, use your federal return’s filing status for your state return.

Illinois income tax rates

The individual tax rate for 2019 is 4.95%.

Illinois deductions and credits to know

Illinois requires a long list of income adjustments for state tax purposes. You may have to pay Illinois state tax on some types of income that aren’t taxable on your federal return. But the state also offers a number of “subtractions” that could help reduce the amount of tax you owe.

Illinois state tax deductions

Some deductions for individuals include the following:

• Personal exemption of $2,275 per filer (and spouse, if filing jointly), which is subject to base income limits by filing status
• There is an additional $1,000 exemption for filers who are 65 or older or legally blind (and their spouses, if filing jointly)
• Contributions made to certain college savings plans
• Military pay
• Distributions from certain state college savings plans (if reported as income on your federal return in order to claim the American opportunity or lifetime learning credits)

To claim deductions, you’ll need to complete Schedule M Other Additions and Subtractions for Individuals and file it with your Form IL-1040.

Illinois state tax credits

Some credits for individual taxpayers include the following:

• Property tax credit: If you own a home in Illinois, you may be able to take the Illinois Property Tax Credit for up to 5% of the Illinois real estate tax you paid on your principal residence. You must meet income limitations to claim this credit.
• Earned income tax credit: For 2019, this credit is worth 18% of your federal earned income credit, if you qualified for it.
• K-12 education expense credit: If you had qualifying education expenses, you may be eligible for a credit of up to $750 per family.

How to file your Illinois state tax return

There are four options to file.

• File with tax-preparation software.
• E-file through the state’s free online service, MyTax Illinois.
• File with the assistance of a tax professional.
• Send a paper return by U.S. mail.

If your paper return includes a payment, send it to …

Illinois Department of Revenue

P.O. Box 19027
Springfield, IL, 62794-9027

If your paper return does not include a payment, send it to …

Illinois Department of Revenue

P.O. Box 19041
Springfield, IL, 62794-9041

If you owe and can’t pay

If you don’t pay the tax that you owe by the due date, the state can assess penalties and add interest charges. Publication 103 Penalties and Interest for Illinois Taxes has the details.

You can request an installment plan by completing Form CPP-1, Payment Installment Plan Request. If the amount you need to pay off exceeds $5,000 (including tax, penalties and interest), you’ll also need to file an additional form. And you can only get a payment plan if you’re current on your filing obligations.

Tracking your Illinois state tax refund

You can track your refund at Where’s My Refund? and with the Illinois Comptroller’s Find Your Illinois Tax Refund System.

If you lost or misplaced your paper refund check, or you didn’t receive your check within 10 days after it was mailed, call the Comptroller’s Office at 1-800-877-8078.

Bottom line

The state of Illinois collected nearly $22 billion in individual income taxes in fiscal year 2019. And although its tax system may seem simple, with just a single flat rate and no tax brackets, figuring the Illinois state deductions and credits that you’re eligible for could be a challenge.

Jennifer Samuel, senior tax product specialist for Credit Karma, has more than a decade of experience in the tax preparation industry, including work as a tax analyst and tax preparation professional. She holds a bachelor’s degree in accounting from Saint Leo University. You can find her on LinkedIn.