A Nassau County property tax grievance is a free annual challenge you file with the Assessment Review Commission (ARC) asking the county to lower the assessed value it uses to calculate your tax bill. For the 2026 tax year, the filing window runs from January 2 through March 31, 2026, after an extension from the original March 2 deadline. The single most important thing to know before you decide: the ARC can lower your assessment or leave it where it is, but it cannot raise it because you filed.1Hempstead Town, NY. Challenge and Lower Your Taxes There is no financial risk to filing.
When and How to File
The 2026 filing window opens January 2, 2026 and closes March 31, 2026.1Hempstead Town, NY. Challenge and Lower Your Taxes Nassau County has granted extensions in past years, but don’t rely on one. Miss the deadline and you lose the right to challenge that year’s assessment entirely; there is no late-filing process for individual applicants.
You have three ways to submit:
- Online through AROW (Assessment Review on the Web). Create an account, link your property using its Section, Block, and Lot (SBL) number, and upload your form and documents. The system issues a confirmation that serves as proof of timely filing.2Nassau County, NY. Assessment Review Commission
- By mail to the Assessment Review Commission, 240 Old Country Road, 5th Floor, Mineola, NY 11501. The postmark must be no later than the deadline; use certified mail with return receipt.1Hempstead Town, NY. Challenge and Lower Your Taxes
- In person at the same Mineola address during business hours. Call (516) 571-3214 to request a paper application if you need one.3Town of North Hempstead. Grievances and Assessment
The form is Form RP-524, Complaint on Real Property Assessment.4New York State Department of Taxation and Finance. Form RP-524 – Complaint on Real Property Assessment You’ll need your SBL number from your tax bill or the county’s Land Records Viewer,5Nassau County. Land Records Viewer your current assessed value, and your own estimate of the property’s market value as of January 2, 2026. That January 2 taxable status date is the valuation point the ARC uses, so any comparable sales or appraisals should reflect values near that date.6Nassau County. Notice of Tentative Assessed Value
Who Can File
You can file if you’re the owner on the deed. You can also authorize someone else in writing to file for you, and that written authorization must be dated within the same calendar year as the complaint.7New York State Senate. New York Real Property Tax Law 524 – Complaints With Respect to Assessments Attorneys and tax grievance firms handle filings this way; the signed authorization has to be attached.
Condo unit owners have an extra option. The board of managers can file a single complaint on behalf of all unit owners, acting as their agent.7New York State Senate. New York Real Property Tax Law 524 – Complaints With Respect to Assessments Individual unit owners can still file separately if they prefer.
What Makes a Valid Grievance
Your complaint has to state at least one of four grounds: the assessment is excessive, unequal, unlawful, or the property is misclassified. The complaint also has to include your own estimate of the property’s value. That estimate isn’t a formality. The ARC treats it as your opening position.
Most residential filers are in Class 1 (one-, two-, and three-family homes, small residential condos, and residentially zoned vacant land). Verify your class on your assessment notice before filing, because filing under the wrong class can get your complaint dismissed quickly.
Evidence That Actually Helps
The RP-524 is straightforward. What determines whether the ARC reduces your assessment is the evidence you attach.
Comparable Sales
The strongest evidence is recent sales of homes similar to yours that sold for less than what the county says your home is worth. Three to five solid comparables that sold within roughly a year of the taxable status date give the ARC real data to work with. Match on square footage, bedroom and bathroom count, lot size, and condition. One truly similar comp beats five that only vaguely resemble your home.
Recent Purchase Price
If you bought the property recently in a normal arm’s-length transaction, not between family members or under foreclosure pressure, the purchase price is often the most persuasive evidence of market value. The RP-524 asks about this directly.
Appraisal
A formal appraisal by a licensed appraiser typically costs between $500 and $1,300. It’s worth considering if your home has features that make standard comparisons difficult, such as unusual layouts, deferred maintenance, or environmental issues.
Photos and Defect Documentation
Photographs of physical defects, contractor estimates for needed repairs, and documentation of conditions that hurt value (flooding history, nearby commercial nuisances) all help. If the assessment doesn’t reflect structural problems or outdated systems, this is where you show that gap.
What Happens After You File
The ARC assigns examiners to review your RP-524 against the county’s own data. There is no hearing and you don’t appear in person; the examiner works from the paper record.
If the ARC agrees a reduction is warranted, it issues a settlement offer at a lower assessed value. Offers typically arrive six to fifteen months after the filing deadline, so plan on a wait. Accepting the offer locks in the new assessment for the upcoming tax cycle, and the reduction flows through to your school tax and general tax bills. If the ARC finds no basis for a reduction, it issues a final determination keeping the original assessment.
If the ARC Denies Your Grievance
A denial isn’t the end. Owners of one-, two-, or three-family homes used as residences can file a Small Claims Assessment Review (SCAR) petition, which moves the dispute to a hearing before a court-appointed hearing officer.8New York Courts. Small Claims Assessment Review (SCAR) The filing fee is $30.
SCAR petitions must be filed within 30 days of the filing of the final assessment roll or the notice of that filing, whichever is later.9New York State Department of Taxation and Finance. Grievance Procedures Watch your mail after the ARC’s denial; that 30-day window is strict.
SCAR hearings are intentionally informal compared to a full tax certiorari proceeding. You and a representative of the assessing unit each present evidence, and the hearing officer decides. You can represent yourself. Organized comparable sales data and, when possible, an appraisal strengthen your position.
Doing It Yourself vs. Hiring a Firm
Many homeowners file successfully on their own. The RP-524 is not complicated, comparable sales are publicly available through the Land Records Viewer, and AROW walks you through the submission. For a straightforward single-family home in a neighborhood with plenty of recent sales, self-filing works.
Tax grievance firms handle the entire process from pulling comparables through filing and negotiating with the ARC. Fee structures vary. Some charge on contingency (a percentage of your first-year tax savings), others charge flat fees, and some require multi-year contracts. A contingency arrangement where you pay nothing if the grievance fails is usually the safest structure for a homeowner. Read the contract before signing; watch for multi-year lock-ins and for fees that apply even on minimal reductions.
Professional help tends to pay off most clearly on higher-value properties, homes with major defects, misclassification cases, or situations where comparable sales are scarce and the analysis takes more judgment.
After a Successful Reduction
Your Mortgage Escrow
If your lender escrows for property taxes, your annual bill drops after a successful grievance, but your monthly escrow payment won’t adjust automatically. Mortgage servicers are required to conduct an annual escrow analysis, and any surplus from overpayment is refunded or credited at that time. To speed things up, send your servicer documentation of the reduced assessment and ask for a mid-cycle recalculation. Some will do it; others wait for the annual review.
Federal Tax Treatment of a Refund
If you itemize and previously deducted your full property tax, a refund from a successful grievance may be partially taxable. Under the tax benefit rule, you generally include a recovered amount in gross income to the extent it reduced your tax liability in the prior year.10Internal Revenue Service. Recovery of Tax Benefit Items If you took the standard deduction, or if your state and local tax deduction was already capped so the refunded portion gave you no benefit, the refund generally carries no federal tax consequence. Nassau County property taxes alone often push filers to the SALT cap, so this situation is common.
File Again Next Year
Nothing stops you from filing every year. Assessment rolls are recalculated annually and market conditions change. A reduction one year doesn’t guarantee a low assessment the next. Treating the grievance as an annual check, rather than a one-time project, is how Nassau County homeowners keep their tax bills accurate over time.