An Illinois Eviction Complaint is a legal document that is used to initiate the eviction process in the state of Illinois. It is typically initiated by a landlord against a tenant, and is the first step in the formal eviction process. There are two types of Illinois Eviction Complaints: a Complaint for Possession and a Complaint for Forcible Entry and Detained. A Complaint for Possession is used when a tenant has failed to pay rent or has violated the terms of the lease, while a Complaint for Forcible Entry and Detained is used when a tenant has wrongfully entered a property or has refused to leave after the lease has expired. In either case, the landlord must file the appropriate complaint with the court in order to start the eviction process.