In Cook County, the due date for the First Installment property taxes is always the first business day in March. A law passed by the Illinois Legislature in 2009 raised the First Installment tax from 50% to 55% of the prior year's total tax (or 55% of the adjusted tax if an assessment certificate of error is certified by the previous November 30).
The due date for the Tax Year 2015 First Installment was Tuesday, March 1, 2016.
The Second Installment due date varies. This is because the Second Installment bill relies on the delivery of various sets of data by other state and county agencies. Unlike the First Installment bill, the Second Installment bill reflects the new assessed values, assessment appeals, exemptions, the state equalization factor, and taxing-district tax rates. All of these data are prepared by other state and county agencies.
The due date for the Tax Year 2014 Second Installment was Monday, August 3, 2015.
NOTE ON PREPAYMENTS: Taxpayers who want to prepay the First Installment tax bill for the following tax year must send a written request for a "Prepayment" tax bill to the Treasurer's Office in December. Taxpayers should never combine the Second Installment from one tax year with payment of the First Installment for the following year. A separate payment must be submitted after obtaining the appropriate "Prepayment" bill.
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