In the City of Chicago, property taxes are paid in arrears. This means that property tax amounts are due the year after the tax year has passed. When a Buyer and Seller are working on their property sale, the property tax proration is a negotiated term. Because taxes are paid in arrears, the parties will not yet have received the property tax bill for the current year by the time of the closing. With each subsequent year, taxes go up. For this reason, the seller will usually pay 105+% of the previous year’s tax bill.