By law, each property, other than farmland, must be viewed, inspected, and revalued once every four years (every three years in Cook County). Farmland is reassessed each year. Between these general assessments, assessors may revalue property if its value is incorrect. Some counties are divided into assessment districts and one section is reassessed each year on a rotating basis. For more information see
Illinois Property Tax Code, 35 ILCS 200/9-155 , 9-160, 9-220, and 9-225.