You must file
Form IL-990-T, Exempt Organization Income and Replacement Tax Return, if you are an organization exempt from federal income tax by reason of Section 501(a) of the Internal Revenue Code (IRC) and earn or receive unrelated business taxable income as determined under IRC, Section 512, and
- have net income as defined under the
Illinois Income Tax Act (IITA) or
- are a resident or qualified to do business in the state of Illinois and are required to file U.S. Form 990-T (regardless of net income or loss).
IL-990-T Instructions for due dates and filing requirements.