This is frustrating. According to the link below, you can access the Form IL 1040 form and start filing:
https://www2.illinois.gov/rev/forms/incometax/Documents/currentyear/individual/il-1040.pdf
Why hasn't ATX updated the software with it yet? Ditto the Form IL 1120-ST....can't we get started on these, already? Come on, ATX. What's the hold up?