765 ILCS 5/35d
In a county with 3,000,000 or more inhabitants, whenever any deed or instrument of conveyance is executed, the grantor of residential property shall provide the grantee of the property with an individual permanent index number or numbers that specifically represent the legal description provided for in the deed or instrument of conveyance. If the individual permanent index number or numbers do not specifically represent the legal description in the deed or instrument of conveyance, the grantor shall provide one of the following:
If the grantor fails to provide the grantee with either a permanent index number or numbers that represent the legal description found in the deed or instrument of conveyance or one of the documents listed in subdivision (1), (2), or (3), the grantor shall be personally liable to the grantee for taxes pursuant to Section 1-145 of the Property Tax Code and attorney's fees. The grantor's liability shall continue to accrue until the permanent index number or numbers that represent the legal description found in the deed or instrument of conveyance or one of the documents listed in subdivision (1), (2), or (3) is delivered to the grantee. The grantor's failure to provide the permanent index number or numbers shall not invalidate the deed or instrument of conveyance. A receipt from the county assessor confirming that a proper application has been filed and that it meets the requirements set by the county assessor shall be deemed to be evidence of proper application for division.
765 ILCS 5/35d