(35 ILCS 200/10-31)
    Sec. 10-31. Subdivisions; counties of less than 3,000,000.
    (a) In counties with less than 3,000,000 inhabitants, the platting and subdivision of property into separate lots and the development of the subdivided property with streets, sidewalks, curbs, gutters, sewer, water and utility lines shall not increase the assessed valuation of all or any part of the property, if:
        (1) The property is platted and subdivided in
accordance with the Plat Act;
        (2) The platting occurs after January 1, 1978;
        (3) At the time of platting the property is in excess
of 5 acres; and
        (4) At the time of platting or replatting the
property is vacant or used as a farm as defined in Section 1-60.
    (b) Except as provided in subsection (c) of this Section, the assessed valuation of property so platted and subdivided shall be determined based on the assessed value assigned to the property when last assessed prior to its last transfer or conveyance. An initial sale of any platted lot, including a lot that is vacant, or a transfer to a holder of a mortgage, as defined in Section 15-1207 of the Code of Civil Procedure, pursuant to a mortgage foreclosure proceeding or pursuant to a transfer in lieu of foreclosure, does not disqualify that lot from the provisions of this subsection (b).
    (c) Upon completion of a habitable structure on any lot of subdivided property, or upon the use of any lot, either alone or in conjunction with any contiguous property, for any business, commercial or residential purpose: (i) the provisions of subsection (b) of this Section shall no longer apply in determining the assessed valuation of the lot, (ii) each lot shall be assessed without regard to any provision of this Section, and (iii) the assessed valuation of the remaining property, when next determined, shall be reduced proportionately to reflect the exclusion of the property that no longer qualifies for valuation under this Section. Holding or offering a platted lot for initial sale shall not constitute a use of the lot for business, commercial or residential purposes unless a habitable structure is situated on the lot or unless the lot is otherwise used for a business, commercial or residential purpose. The replatting of a subdivision or portion of a subdivision does not disqualify the replatted lots from the provisions of subsection (b).
    (d) This Section applies on and after the effective date of this amendatory Act of the 96th General Assembly and through December 31, 2011.
(Source: P.A. 96-480, eff. 8-14-09.)