Your Illinois filing period is the same as your federal filling period. In general, Form
IL-990-T is due on or before the 15th day of the
5th month following the close of the tax year. If you are an employee trust as described in IRC Section 401 (a), you must file Form IL-990-T on or before the 15th day of the
4th month following the close of the tax year.
You are not required to file Form
IL-505-B, Automatic Extension Payment, in order to obtain this automatic extension. However, if you expect tax to be due, you must use Form IL-505-B to pay any tentative tax due in order to avoid interest and penalty on tax not paid by the original due date of the return. An extension of time to file your Form IL-990-T does not extend the amount of time you have to pay your Illinois tax liability.
