Online Homestead Exemption filing for tax year 2025 is open. Exemption applications must be filed with your local assessor's office.See our Municipal Profiles for your local assessor's mailing address. No information is available for this page. For further information or to obtain an application call 516-571-1500 or visit the Nassau County Assessor's website. To qualify for Homestead Exemption (F. For all of the abovelisted exemptions, you can fill out and submit a Nassau County exemption form today! File a Tax Grievance. I just purchased a home in Nassau County, NY and would like to finish the basement. My understanding is that the.