The Illinois Cook County Assessor's Office 2017 Class 9 Affidavit is a legal document used to certify the value of a property in Cook County, Illinois. It is used to document the information regarding the assessed value of a property, such as the owner, the assessed value, the date of assessment, and the tax rate. The affidavit is signed by the Cook County Assessor and is witnessed by the County Clerk. There are two types of Illinois Cook County Assessor's Office 2017 Class 9 Affidavit: a residential affidavit and a commercial affidavit. The residential affidavit is used for properties that are used as a primary residence, while the commercial affidavit is used for properties used for business purposes. Both affidavits require the property owner to provide information about the property, such as the address, the assessed value, and the property classification. The affidavit must be filed with the Cook County Assessor's Office in order to be valid.