Legal Question in Tax Law in Illinois

There's a statue of limitations on collection which runs, generally, ten years from the "date of assessment."

Certain actions may suspend the statute for a period of time, those actions including filing of an Offer in Compromise, submitting a Collection Due Process Appeal request, filing a bankruptcy, etc.

Generally ten years, but remember it's measured from the date of assessment, not ten years from the end of the tax year or tax period.