Contact your county treasurer for payment due dates. The phone number should be listed in your local phone book under Government, County Assessor's Office or by searching online.
In most counties, property taxes are paid in two installments, usually June 1 and September 1. If the tax bills are mailed late (after May 1), the first installment is due 30 days after the date on your tax bill. County boards may adopt an accelerated billing method by resolution or ordinance.
Cook County and some other counties use this billing method. Under this system, the first installment of taxes is 55 percent of last year’s tax bill. This installment is mailed by January 31. In Cook County, the first installment is due by March 1. (Elsewhere, a county board may set a due date as late as June 1.) The second installment is prepared and mailed by June 30 and is for the balance of taxes due. The balance is calculated by subtracting the first installment from the total taxes due for the present year. The second installment is due August 1.