735 ILCS 5/9-202
If any tenant or any person who is in or comes into possession of any lands, tenements or hereditaments, by, from or under, or by collusion with the tenant, wilfully holds over any lands, tenements or hereditaments, after the expiration of his or her term or terms, and after demand made in writing, for the possession thereof, by his or her landlord, or the person to whom the remainder or reversion of such lands, tenements or hereditaments belongs, the person so holding over, shall, for the time the landlord or rightful owner is so kept out of possession, pay to the person so kept out of possession, or his or her legal representatives, at the rate of double the yearly value of the lands, tenements or hereditaments so detained to be recovered by a civil action.
735 ILCS 5/9-202