The filing of a federal tax return has little to do with your requirement to file a state, and usually has nothing to do with it. However, in most cases, if you are not required to file a federal return, you need not file a state return.
To be sure, check out the instructions to the state return. I have attached a link to the IL instructions for the IL-1040.
Marty Davidoff, email@example.com, 732-274-1600. This answer is provided for general information only. You should seek advice from an attorney or tax professional.
If you have to file a Federal Tax return you most likely will have to file a State Income tax return. It is probably not a bad idea to file one anyway if you file a Federal tax return. Otherwise, the statute of limitations does not begin to run. However, the actual filing requirement is determined by your state and has nothing to do with the requirement of a Federal income tax return. Perhaps one of our IL attorneys can comment on this portion of your question.
Any individual seeking legal advice for their own situation should retain their own legal counsel as this response provides information that is general in nature and not specific to any person's unique situation. Circular 230 Disclaimer - Advice given in this response cannot be used to eliminate penalties with the IRS or any other governmental agency.
I agree with Attorney Lively. It never hurts to file your return. You can never be worse off by doing so.