Amends the Property Tax Extension Limitation Law in the Property Tax Code. Provides that a taxing district shall reduce its aggregate extension base for the purpose of lowering its limiting rate for future years upon referendum approval initiated by the submission of a petition by the voters of the district. Provides that the extension limitation shall be: (a) the lesser of 5% or the average percentage increase in the Consumer Price Index for the 10 years immediately preceding the levy year for which the extension limitation is being calculated; or (b) the rate of increase approved by the voters. Effective immediately.