35 ILCS 200/9-185
The purchaser of property on January 1 shall be considered as the owner on that day. However, when a fee simple title or lesser interest in property is purchased, granted, taken or otherwise transferred for a use exempt from taxation under this Code, that property shall be exempt from taxes from the date of the right of possession, except that property acquired by condemnation is exempt as of the date the condemnation petition is filed. Whenever a fee simple title or lesser interest in property is purchased, granted, taken or otherwise transferred from a use exempt from taxation under this Code to a use not so exempt, that property shall be subject to taxation from the date of purchase or conveyance. It shall be the obligation of the titleholder of record in such cases where there is a change in use or a change in a leasehold estate or, in cases where there has been a purchase, grant, taking or transfer, it is the obligation of the transferee to notify the chief county assessment officer within 30 days of that action. Failure to give the notification, resulting in the assessing official continuing to list the property as exempt in subsequent years, shall cause the property to be considered omitted property for the purpose of this Code. In those cases the county collector is authorized to issue a tax bill to the person holding title to the property in that part of the year during which it was not exempt from taxation for that part of the year and to accept payment of the bill as full and final settlement of tax liability for the year involved.
35 ILCS 200/9-185