The Illinois Legislature previously passed legislation that temporarily changed the first installment due date for 2010 Cook County real estate taxes, which are payable in 2011. The 2010 Cook County first installment real estate tax due date is April 1, 2011 (not March 1, 2011) and 2010 first installment real estate tax bills are scheduled to be mailed by the Treasurer today. This is a one-time change by the Illinois Legislature to lessen the close proximity of the 2009 Cook County second installment real estate tax due date and the 2010 first installment real estate tax due date. Cook County first installment real estate tax due dates will revert back to March 1 in 2012 and subsequent years.