Guide · Sources reviewed September 20, 2026

The Nassau County tax grievance form: filing online with ARC

Filing with ARC is free and does not require an attorney. Gather your County record, your view of the value, and supporting files first, follow the County’s current instructions, and keep the confirmation.

Before you open the form

Gather these so you are not hunting for them with the window closing:

• Your County record. The parcel identifier (section, block, and lot as the County records them) plus the assessment year you are appealing and the market and assessed values shown. Our property checker is a starting point; confirm with the County’s own record.
• The owner’s name as recorded. The application is made by the owner or by someone the owner authorizes, so know which of those you are and whether anyone else already has an authorization for this year.
• Your view of the value, and why. Expect to be asked what you believe the property is worth. Our comparable sales guide covers how to support that figure honestly.
• Supporting documents as files. An appraisal, photographs, a recent sale contract, an inspection report, or permits, in a format you can upload if the County’s system asks for attachments.
• An email address you check. If the system offers to send confirmations electronically, you want them to arrive somewhere you will see.

The filing, step by step

This is how the steps have looked in recent years. Where the County’s instructions describe a step differently, follow the County.

1. Register and find your home. Create an account from the County’s instructions page, look up your address, and check that the description of your home is largely right.
2. Choose comparable sales. The system offers sales near you. Practitioners recommend starting with the first five it suggests, keeping only ordinary sales from about the last two years. You can add other sales with the search (magnifying glass) button. Our comparable sales guide explains how to judge them at the County’s level of assessment.
3. Fill in Part D, the other facts. List what lowers your home’s value that the record does not show: needed repairs (with estimates), outdated kitchens or baths, a flood zone, a busy road. If you bought within about three years, or have listed the home, for less than the price your County value stands for, say so. Do the arithmetic in dollars, for example “I could not sell this home for $930,000.”
4. Submit, then upload. After you submit, the system offers an upload button for photographs, repair estimates, an appraisal, or a sale contract.
5. Keep the confirmation. Nothing is filed until you have the appeal number or confirmation email.

ARC issues its decisions through March 31, 2028, so expect a long wait. Our guide to ARC’s decision covers what comes back.

Representatives and duplicate filings

You can file for yourself or authorize a representative to file for you, not both. Duplicate applications and overlapping authorizations create avoidable problems, so if a firm, a prior owner, or a condominium board may already be filing for this assessment year, settle that first. The County’s instructions cover both routes. If your property is assessed by a village or city, that assessment has a separate local appeal process, which the County FAQ explains.

After you submit

ARC will either reduce your assessment or leave it unchanged; the County states it will never increase the assessment. Our guide on whether filing can raise your assessment quotes the County’s wording. Keep your confirmation, the labeled record you filed against, and your evidence together. If ARC’s outcome does not satisfy you, Small Claims Assessment Review is the optional next step, with its own fee and a short deadline.

Good Grieves does not file applications with the County through this website, does not authorize representation, and does not guarantee savings. This page is general information, not legal advice.