The Illinois Cook County assessor's Office 2017 Class S affidavit is a document that is used by property owners in Cook County, Illinois to appeal their assessed value of their property for the 2017 tax year. This affidavit is used to provide evidence that the property was over-assessed, so the owner can receive a lower tax bill. There are three types of Illinois Cook County assessor's Office 2017 Class S affidavit: Residential, Commercial/Industrial, and Vacant/Unimproved. The affidavit must include information such as the name of the property owner, the property address, and the assessed value of the property. The affidavit must also include supporting documents such as a copy of the most recent tax bill, a copy of the deed, and other documents that prove the assessed value is too high. Once the affidavit is signed and submitted to the assessor's office, the assessor will review it and make a decision on whether to reduce the assessed value.