(a) A county that has by ordinance approved an economic development plan, established an economic development project area, and adopted tax increment allocation financing for that area shall file certified copies of the ordinance or ordinances with the county clerk. Upon receiving the ordinance or ordinances, the county clerk shall immediately determine (i) the most recently ascertained equalized assessed value of each lot, block, tract, or parcel of real property within the economic development project area from which shall be deducted the homestead exemptions under Article 15 of the Property Tax Code (that value being the “initial equalized assessed value” of each such piece of property) and (ii) the total equalized assessed value of all taxable real property within the economic development project area by adding together the most recently ascertained equalized assessed value of each taxable lot, block, tract, or parcel of real property within the economic development project area, from which shall be deducted the homestead exemptions under Article 15 of the Property Tax Code, and shall certify that amount as the “total initial equalized assessed value” of the taxable real property within the economic development project area.
     (b) After the county clerk has certified the “total initial equalized assessed value” of the taxable real property in the economic development project area, then in respect to every taxing district containing an economic development project area, the county clerk or any other official required by law to ascertain the amount of the equalized assessed value of all taxable property within the taxing district for the purpose of computing the rate per cent of tax to be extended upon taxable property within the taxing district shall, in every year that tax increment allocation financing is in effect, ascertain the amount of value of taxable property in an economic development project area by including in that amount the lower of the current equalized assessed value or the certified “total initial equalized assessed value” of all taxable real property in the area. The rate per cent of tax determined shall be extended to the current equalized assessed value of all property in the economic development project area in the same manner as the rate per cent of tax is extended to all other taxable property in the taxing district. The method of extending taxes established under this Section shall terminate when the county adopts an ordinance dissolving the special tax allocation fund for the economic development project area. This Act shall not be construed as relieving property owners within an economic development project area from paying a uniform rate of taxes upon the current equalized assessed value of their taxable property as provided in the Property Tax Code.