Illinois — Automatic Extension Payment for Individuals Filing Form IL-1040
More about the Illinois Form IL-505-I Extension
We last updated Illinois Form IL-505-I in January 2026 from the Illinois Department of Revenue. This form is for income earned in tax year 2025, with tax returns due in April 2026. We will update this page with a new version of the form for 2027 as soon as it is made available by the Illinois government.
Other Illinois Individual Income Tax Forms:
In addition to information about Illinois' income tax brackets, Tax-Brackets.org provides a total of 76 Illinois income tax forms, as well as many federal income tax forms. Here's a list of some of the most commonly used Illinois tax forms:
| Form Code | Form Name |
|---|---|
| Form IL-1040-PTR | ​Property Tax Rebate Form |
| Form IL-1040 | Individual Income Tax Return |
| Schedule ICR | Illinois Tax Credits |
| Schedule NR-1040 | Nonresident and Part-Year Resident Computation of Illinois Tax |
| Form IL-1040-ES | Estimated Income Tax Payments for Individuals |
View all 76 Illinois Income Tax Forms
Disclaimer: While we do our best to keep Form IL-505-I up to date and complete on Tax-Brackets.org, we cannot be held liable for errors or omissions. Is this form missing or out-of-date? Please let us know so we can fix it!
Tax Form Sources:
- Illinois Department of Revenue ( https://www2.illinois.gov/rev/Pages/default.aspx
) - Department of Revenue Income Tax Forms ( https://www2.illinois.gov/rev/forms/Pages/default.aspx )