Summary. In April 2023, Cook County prioritized three research questions regarding Illinois' homestead exemptions for further study. Each year applicants must complete and file Form PTAX-340 with the Chief County Assessment Officer.Homestead exemption applications must be filed annually between February 2 and June 30. Application forms are typically available beginning February 2. Select all exemption(s) for which you are applying: Basic Homestead Exemption. Finally, remember that you must apply for the exemption with the County Assessment Office.