Guide · Sources reviewed September 20, 2026

How to choose a Nassau County tax grievance company

You never need a company to file with ARC. If you hire one, read the service agreement as closely as the ARC authorization, sign only one authorization per year, and ask what happens after ARC decides.

What a grievance firm actually does

A representative does the same work you could do yourself, on your behalf and usually across many properties at once:

• Reviews your record. It reads the County’s tentative assessment for your home and looks for errors in the recorded details.
• Builds the evidence. It selects comparable sales and prepares a claimed value. Our comparable sales guide describes the same work.
• Files the application. It submits your Application for Correction of Assessment with ARC during the filing window, under a representative number the County requires it to obtain.
• Handles ARC’s response. The County states that once you designate a representative, ARC may speak only to the representative, so offers of reduction go to the firm.
• May go further. Some firms pursue Small Claims Assessment Review if ARC’s result is not satisfactory; others do not. Ask.

The two documents you sign

Hiring a representative usually means signing two things, and it helps to keep them apart.

The ARC authorization is the County’s requirement. It lets the firm file for one property for one tax year. ARC’s published requirements for 2028–29 authorizations, linked from its representative page, say the authorization must name the 2028–29 tax year (a calendar year alone is not enough), identify the property by section, block, and lot, name the representative and its ARC number, be dated by you rather than pre-printed, and be dated no more than 120 days before the first filing date. The County’s FAQ adds that an authorization is valid for only one filing.

The service agreement is the firm’s own contract with you. It sets the fee, when it is owed, whether the arrangement renews each year, and how to cancel. The County neither writes nor enforces it. This is the document to read slowly.

How firms charge

Representatives generally charge a percentage of your first-year savings, a flat fee, or a hybrid of the two. A percentage fee often costs nothing up front and rises with the reduction; a flat fee is known in advance and does not rise with the reduction, but is owed even when the savings are small. Neither is automatically better: it depends on a result nobody knows before ARC decides. Our comparison of Nassau grievance companies quotes each firm’s published fee, and our cost guide compares the structures with a calculator and lists the fee questions to ask before signing.

Questions to ask any firm

• Who files, and are they registered with ARC? The County requires representatives filing for owners to register and obtain a representative number.
• Does the agreement renew every year? If so, how do you stop it, by when, and in what form?
• Who decides on an offer of reduction? ARC talks to the representative. Will the firm ask you before accepting, and how quickly will it tell you?
• Is SCAR included? If ARC leaves the assessment unchanged, will the firm file a SCAR petition, and does it charge extra beyond the $30 filing fee?
• What is not covered? Village and city assessments, and exemption applications, are separate processes. Ask whether the firm handles either.
• What do they need from you? Photographs, details of recent work, or a recent appraisal can all matter, and a firm that asks for them is doing the work.

Switching firms or cancelling

For a new assessment year, the County’s instructions are clear: if you hired a representative to challenge a prior assessment, you are free to change representatives or file for yourself. The ARC authorization does not carry forward; the service agreement might. Give whatever notice the agreement requires, in writing, and keep a copy.

Mid-year is harder. If a firm has already filed for the current year, a second filing by you or another firm is a duplicate. Contact the firm and ARC before filing anything, and let the application already on file be withdrawn or resolved first.

Duplicate filings and early solicitations

Nassau County warns about this directly. Its instructions say that many grievance services seek an authorization in advance of the filing period; that if you represent yourself you should not sign one; that if you hire a representative you should not sign more than one; and that unresolved duplicate applications will be denied. A duplicate does not just waste one filing: it can put the whole year’s appeal at risk.

Before signing, check whether you or a previous owner already authorized someone for the coming year. If you own a condominium, ask whether the board of managers files for the building, since the County advises against filing yourself in that case.

Signs to slow down

None of these proves a firm is acting in bad faith, but each is a reason to read carefully before signing:

• An authorization with no tax year, no property identifier, or a date already filled in. The County requires the signer to date it.
• A promise of a specific reduction or dollar saving. ARC decides the outcome.
• A fee that is described loosely, such as “a share of savings,” with no written definition of savings or of when it is owed.
• Pressure to sign quickly, or a mailer that leaves you unsure whether it came from a private firm or from the County. ARC does not charge to file.
• No clear way to cancel, or an agreement that renews without saying so.

Filing yourself is a real option

The County designed the ARC process for homeowners. It has run community grievance workshops and posts a video of its workshop presentation, and our process guide and deadline guide walk through the steps. A representative is worth paying for when it saves you time or brings judgment you do not have, not because the County requires one.

Good Grieves charges a flat $200 service fee with no percentage of savings, and nothing if there is no reduction. The questions above apply to us as much as to anyone. This page is general information, not legal advice; if an agreement is unclear, ask a lawyer to read it.