The U.S. Department of Education posts state deadlines for FAFSA completion on October 1st of each year for the coming school year. See the 2018-2019 schedule.
DOEd recommends that Illinois college students and families complete the FAFSA as soon as possible after the October 1st start date because Illinois colleges determine financial aid awards until funds are depleted. Each college can have a different FAFSA deadline, so check with colleges that you are interested in attending and clarify whether they are stating the date of FAFSA receipt or processing.
If you need assistance, CFAST offers college planning services that help you through every step of college application, funding and continued support while attending college. Attend one of our free seminars to answer your questions and get advice based on our experience.