Illinois Property Age Change Affidavit is a legal form used to change the age of a property in the state of Illinois. It is a sworn statement made by the owner of a property to the County Recorder, which states that the property has been in the same ownership for at least 10 years. The affidavit is used to change the age of a property for the purpose of determining the real estate tax rate. There are two types of Illinois Property Age Change Affidavit: Affidavit of Ownership and Affidavit of Transfer. The Affidavit of Ownership is used when a property has been owned by the same owner for at least 10 years. The Affidavit of Transfer is used when the property has been transferred between owners within the last 10 years. Both affidavits are signed and notarized by the property owner before they are submitted to the County Recorder.