Illinois will not allow letter rulings to be relied upon once the letter ruling is ten years old.

It is stated, “No ruling may be cited or relied upon for any purpose after the date of its revocation, and the ruling will cease to bind the Department after the date of revocation.” Taxpayers must apply for a new ruling prior to their previous ruling expiring in order to avoid risking being out of compliance with the state. (Title 2 Part 1200 Section 1200.110(e), effective April 11, 2002.)