The forms for this filing are available at the Property Appraiser's office, our website, or at the Department of Revenue's website. Sales of tangible personal property are subject to New York sales tax unless they are specifically exempt.Sales of services are generally exempt. The following answers to frequently asked questions may help you decide whether you should appeal your property's assessment and will guide you on how to do it. Nassau County's deadline to file a property tax grievance is approximately 18 months in advance of the tax year being challenged, barring any extensions. Using your Parcel ID (school district, section, block, and lot numbers) or tax bill number, you may search for your current General and School Tax Bills. The Nassau County Department of Assessment (the Assessor) is requiring the submission of 2023 financial data on a form known as "ASIE2023." Why did my taxes go up? All businesses are required to file annually a Declaration of Personal Property that lists the assets' original cost. Person Filling Out Tax Form.