Section 605 ILCS 5/5-906 - Impact Fee Ordinance or Resolution Requirements(a) An impact fee ordinance or resolution shall satisfy the following 2 requirements: (1) The construction, improvement, expansion or enlargement of new or existing roads, streets, or highways for which an impact fee is imposed must be specifically and uniquely attributable to the traffic demands generated by the new development paying the fee.(2) The impact fee imposed must not exceed a proportionate share of the costs incurred or the costs that will be incurred by the unit of local government in the provision of road improvements to serve the new development. The proportionate share is the cost specifically attributable to the new development after the unit of local government considers the following: (i) any appropriate credit, offset or contribution of money, dedication of land, construction of road improvements or traffic reduction techniques; (ii) payments reasonably anticipated to be made by or as a result of a new development in the form of user fees, debt service payments, or taxes which are dedicated for road improvements; and (iii) all other available sources of funding road improvements.(b) In determining the proportionate share of the cost of road improvements to be paid by the developer, the following 8 factors shall be considered by the unit of local government imposing the impact fee:(1) The cost of existing roads, streets and highways within the service area or areas.(2) The means by which existing roads, streets and highways have been financed to cure existing deficiencies.(3) The extent to which the new development being assessed the impact fees has already contributed to the cost of improving existing roads, streets or highways through taxation, assessment, or developer or landowner contributions paid in prior years.(4) The extent to which the new development will contribute to the cost of improving existing roads, streets or highways in the future.(5) The extent to which the new development should be credited for providing road improvements, without charge to other properties within the service area or areas.(6) Extraordinary costs, if any, incurred in servicing the new development.(7) Consideration of the time and price differential inherent in a fair comparison of fees paid at different times.(8) The availability of other sources of funding road improvements, including but not limited to user charges, general tax levies, intergovernmental transfers, and special taxation or assessments.(c) An impact fee ordinance or resolution shall provide for the calculation of an impact fee in accordance with generally accepted accounting practices. An impact fee shall not be deemed invalid because payment of the fee may result in a benefit to other owners or developers within the service area or areas, other than the person paying the fee.