(35 ILCS 200/18-155)

Sec. 18-155. Apportionment of taxes for district in two or more counties. The burden of taxation of property in taxing districts that lie in more than one county shall be fairly apportioned as provided in Article IX, Section 7, of the Constitution of 1970.

The Department may, and on written request made before July 1 to the Department shall, proceed to apportion the tax burden. The request may be made only by an assessor, chief county assessment officer, Board of Review, Board of Appeals, overlapping taxing district or 25 or more interested taxpayers. The request shall specify one or more taxing districts in the county which lie in one or more other specified counties, and also specify the civil townships, if any, in which the overlapping taxing districts lie. When the Department has received a written request for equalization for overlapping tax districts as provided in this Section, the Department shall promptly notify the county clerk and county treasurer of each county affected by that request that tax bills with respect to property in the parts of the county which are affected by the request may not be prepared or mailed until the Department certifies the apportionment among counties of the taxing districts' levies, except as provided in subsection (c) of this Section. To apportion, the Department shall:

(a) On or before December 31 of that year cause an assessment ratio study to be made in each township in which each of the named overlapping taxing districts lies, using equalized assessed values as certified by the county clerk, and an analysis of property transfers prior to January 1 of that year. The property transfers shall be in an amount deemed reasonable and proper by the Department. The Department may conduct hearings, at which the evidence shall be limited to the written presentation of assessment ratio study data.

(b) Request from the County Clerk in each County in which the overlapping taxing districts lie, certification of the portion of the assessed value of the prior year for each overlapping taxing district's portion of each township. Beginning with the 1999 taxable year, for those counties that classify property by county ordinance pursuant to subsection (b) of Section 4 of Article IX of the Illinois Constitution, the certification shall be listed by property class as provided in the classification ordinance. The clerk shall return the certification within 30 days of receipt of the request.

(c) Use the township assessment ratio studies to apportion the amount to be raised by taxation upon property within the district so that each county in which the district lies bears that burden of taxation as though all parts of the overlapping taxing district had been assessed at the same proportion of actual value. The Department shall certify to each County Clerk, by March 15, the percent of burden. Except as provided below, the County Clerk shall apply the percentage to the extension as provided in Section 18-45 to determine the amount of tax to be raised in the county.

If the Department does not certify the percent of burden in the time prescribed, the county clerk shall use the most recent prior certification to determine the amount of tax to be raised in the county.

If the use of a prior certified percentage results in over or under extension for the overlapping taxing district in the county using same, the county clerk shall make appropriate adjustments in the subsequent year, except as provided by Section 18-156. Any adjustments necessitated by the procedure authorized by this Section shall be made by increasing or decreasing the tax extension by fund for each taxing district where a prior certified percentage was used. No tax rate limit shall render any part of a tax levy illegally excessive which has been apportioned as herein provided. The percentages certified by the Department shall remain until changed by reason of another assessment ratio study made under this Section.

To determine whether an overlapping district has met any qualifying rate prescribed by law for eligibility for State aid, the tax rate of the district shall be considered to be that rate which would have produced the same amount of revenue had the taxes of the district been extended at a uniform rate throughout the district, even if by application of this Section the actual rate of extension in a portion of the district is less than the qualifying rate.

(Source: P.A. 99-335, eff. 8-10-15.)