How Much Do You Have to Make to File Taxes in Illinois?

Illinois state income tax is a financial obligation for many individuals who reside in or earn income from the state.

Determining Your Illinois Filing Requirement

An individual’s obligation to file an Illinois income tax return, Form IL-1040, is determined by their residency status and income level. Full-year residents must file if they are required to submit a federal income tax return. Even without a federal filing requirement, an Illinois resident must file if their Illinois base income surpasses their total exemption allowance. For the 2024 tax year, the personal exemption amount is $2,775 per individual.

For instance, a single resident under 65 must file if their Illinois income exceeds $2,775, while a married couple with no dependents must file if their income is more than $5,550. Individuals claimed as a dependent on another person’s return also have a filing requirement if their Illinois base income is greater than $2,775 or if they seek a refund of Illinois income tax withheld. Special considerations apply to those 65 or older or who are legally blind, as they receive an additional $1,000 exemption each. However, these exemption allowances are not available for high-income taxpayers whose federal adjusted gross income exceeds $250,000 for single filers or $500,000 for married couples filing jointly.

Part-year residents are required to file Form IL-1040 and Schedule NR if they earned income from any source while residing in Illinois. They must also file if they earned income from Illinois sources during their non-residency period, or if they wish to claim a refund of any Illinois income tax withheld. Non-residents must file an Illinois return if they earned sufficient taxable income from Illinois sources to incur a tax liability. Filing is also necessary for non-residents seeking a refund of any Illinois tax erroneously withheld.

Illinois has reciprocal agreements with Iowa, Kentucky, Michigan, and Wisconsin. This means that wages, salaries, and commissions earned by residents of these states working in Illinois are taxed only by their state of residency, not by Illinois. However, other income from Illinois sources earned by residents of these reciprocal states remains taxable by Illinois.

Understanding Illinois Taxable Income

Illinois income tax calculations begin with an individual’s federal adjusted gross income (AGI), which serves as the starting point. The state then requires certain additions to this federal AGI and permits specific subtractions to arrive at the Illinois base income. This modified income figure is then compared against the filing thresholds.

Common additions to federal AGI for Illinois purposes include a child’s federally tax-exempt interest and dividend income if reported on federal Form 8814. Distributive shares of additions from partnerships, S corporations, trusts, or estates are also added back. Additionally, certain earnings from 529 college savings plans that were not included in federal AGI may need to be added.

Conversely, Illinois allows several subtractions from federal AGI, including:
Most retirement income, such as pensions, 401(k)s, individual retirement accounts (IRAs), and certain annuities.
Social Security benefits.
Contributions to qualified Illinois college savings accounts and ABLE accounts.
Military pay.
Illinois income tax refunds included in federal AGI for the current tax year.

Completing and Submitting Your Illinois Tax Return

Once an individual determines they are required to file an Illinois income tax return and has calculated their Illinois taxable income, the next step involves completing and submitting the necessary forms. The primary form for individual income tax is Form IL-1040. If an individual is a part-year resident or non-resident, they will also need to complete Schedule NR, the Nonresident and Part-Year Resident Computation of Illinois Tax.

Taxpayers have several options for filing their Illinois return. Electronic filing is widely encouraged through MyTax Illinois, the Illinois Department of Revenue’s (IDOR) online platform, which offers a free and often faster processing experience. Tax preparation software can also facilitate electronic filing. For those who prefer, paper filing remains an option, with forms available for download from the IDOR website.

The deadline for filing the 2024 Illinois income tax return and paying any tax owed is April 15, 2025. If a taxpayer needs more time to file, Illinois grants an automatic six-month extension, pushing the filing deadline to October 15, 2025. It is important to remember that this extension applies only to the filing deadline, not to the payment deadline. Any tax due must still be paid by April 15, 2025, to avoid potential penalties and interest. Payments can be made electronically through MyTax Illinois using Form IL-505-I, Automatic Extension Payment for Individuals.