This exemption is for individuals who own and occupy their property (as their primary residence), are 65 years or older, and who are liable for the payment of the real estate taxes on the property. 
Eligible senior taxpayers can complete an application at any time during the year that they turn 65 (application can be found here).
Annual renewal cards will be send to qualified taxpayers annually and should be returned to confirm continued eligibility.
This exemption reduces the real estate value by $5,000.

Please contact the Winnebago County Supervisor of Assessments Office (815) 319-4460 with any questions.