35 ILCS 200/9-270
A charge for tax and interest for previous years, as provided in Sections 9-265 or 14-40, shall not be made against any property for years prior to the date of ownership of the person owning the property at the time the liability for the omitted tax was first ascertained. Ownership as used in this section shall be held to refer to bona fide legal and equitable titles or interests acquired for value and without notice of the tax, as may appear by deed, deed of trust, mortgage, certificate of purchase or sale, or other form of contract. No charge for tax of previous years, as provided in Section 9-265, shall be made against any property if (1) the assessor failed to notify the board of review of an omitted assessment in accordance with subsection (a-1) of Section 9-260; (2) the property was last assessed as unimproved, the owner of the property gave notice of subsequent improvements and requested a reassessment as required by Section 9-180, and reassessment of the property was not made within the 16 month period immediately following the receipt of that notice; (3) the owner of the property gave notice as required by Section 9-265; (4) the assessor received a building permit for the property evidencing that new construction had occurred or was occurring on the property but failed to list the improvement on the tax rolls; (5) the assessor received a plat map, plat of survey, ALTA survey, mortgage survey, or other similar document containing the omitted property but failed to list the improvement on the tax rolls; (6) the assessor received a real estate transfer declaration indicating a sale from an exempt property owner to a non-exempt property owner but failed to list the property on the tax rolls; or (7) the property was the subject of an assessment appeal before the assessor or the board of review that had included the intended omitted property as part of the assessment appeal and provided evidence of its market value.
The owner of property, if known, assessed under this and the preceding section shall be notified by the county assessor, board of review or Department, as the case may require.
35 ILCS 200/9-270