815 ILCS 105/12
Current through Public Act 103-593
In any action upon a note, bond, bill, or other instrument in writing, which has been assigned to or transferred by delivery to the plaintiff after it became due, a set-off to the amount of the plaintiff's debt may be made of a demand existing against any person or persons who shall have assigned or transferred such instrument after it became due, if the demand be such as might have been set-off against the assignor, while the note or bill belonged to him.
815 ILCS 105/12