35 ILCS 200/21-50
In the event any property becomes newly liable for taxes levied by any taxing district because of an incorporation or annexation of the taxing district or liability does not exist because of a disconnection of any area of the unit of local government or school district or the dissolution thereof, each estimated installment of property taxes provided for in Section 21-30 shall be computed at 25% of the total of the tax bill for the property for the preceding year. Taxes for which the property becomes newly liable or for which liability does not exist for the property because of a disconnection of any area of, or the dissolution of, any taxing district, shall be added to or subtracted from the balance of taxes due for that year under Section 21-30.
35 ILCS 200/21-50