In any county in which the accelerated method of billing and paying taxes as provided for in Section 21-30 is in effect, if a taxpayer has paid an amount on his or her estimated tax bills which exceeds the total taxes for the year as shown on the actual tax bill, the county collector shall refund the amount of the overpayment to the person who paid the estimated installments.
When a payment in full satisfaction of a year's taxes has been made, but an open balance is shown unpaid on the Warrant Book because of an over estimation of the taxes in the estimated installments, the County Collector shall provide for an appropriate entry in the Warrant Book to close the item.
35 ILCS 200/21-60