The Illinois Department of Revenue will automatically grant you a six-month extension of time to file your tax return. For calendar year filers, the filing date is automatically extended to October 15. You are not required to file Form IL-505-I to obtain this automatic extension. However, you must pay any tentative tax due by the original due date of your return in order to avoid any late-payment penalty and interest on unpaid tax.

You must file Form IL-505-I if all of the following apply to you: you cannot file your tax return by the due date, and you will owe a tentative tax (complete the Tax Payment Worksheet on the back of this page to determine this), and you submit your payment by paper check or money order (i.e., you do not use any electronic means, such as electronic funds transfer, to make your payment).

The purpose of Form IL-505-I, Automatic Extension Payment, is to provide taxpayers who are unable to file their tax return by the due date a means of calculating and remitting their tentative tax liability (including any other taxes you will report on your IL-1040) on or before the original due date of the return

NOTE: An extension of time to file does not extend the amount of time you have to make your payment. If you owe any tentative tax, and you pay with a paper check or money order, file Form IL-505-I along with your payment on or before the original due date of your annual return, or as soon as you realize you owe tentative tax.

WebFile (https://www.revenue.state.il.us/app/eftiit/) is an easy way to pay your IL-505-I payment. If you do not expect to owe tax, you do not have to do anything.

Additional extension beyond six months
If you cannot file your tax return within the automatic six-month extension period, the Illinois Department of Revenue will grant you an extension of more than six months to file only if the Internal Revenue Service (IRS) grants you an additional extension.

For additional information, please visit the State of Illinois Department of Revenue website.

Form IL-505-I (Automatic Extension Payment for Individuals Filing Form IL-1040): http://tax.illinois.gov/TaxForms/IncmCurrentYear/Individual/IL-505-I.pdf

Mail your Form IL-505-I to: Illinois Department of Revenue, P.O. Box 19005, Springfield, Illinois 62794-9005.