A homeowners' exemption may also apply to a supplemental assessment. For more information, call (925) 313-7481.STATEMENTS. This claim may be used to file for the Homeowners' Exemption for the Assessment Roll and the Supplemental Assessment Roll. To qualify for the homeowners' exemption, the home must have been the principal residence of the owner as of January 1 of that tax year. Applying for an exemption. You can apply online for any of these exemptions through the Cook County Assessor's Office. Download PDF BOE-266 REV. To be eligible for the general homestead exemption: •.