In Nassau County, New York, the average property tax rate is 2.10%, which is nearly double the national average of 1.02%.
The tax rate is a percentage of your property’s assessed value. This value is determined by the Nassau County Department of Assessment and is intended to reflect the property's market value. The higher the assessed value, the more taxes you will owe.
However, you don’t have to accept the county’s valuation. You can challenge the assessment by filing a Nassau County tax grievance, which can reduce your assessed value and, in turn, lower your property taxes.
A tax grievance isn’t a lawsuit, so you don’t need a lawyer to represent you. You can file it on your own and enjoy significant tax savings, or hire a company like Ownwell. This guide will explain what a tax grievance is in Nassau County, why you need it, and how to file it step by step.
Nassau County Tax Grievance at a Glance:
What it is: A formal process to challenge your property's assessed value.
Filing Period: Annually, from early January to early March (check for extensions).
2026 Filing Deadline: Monday, March 2, 2026 (for the 2027-2028 tax year).
Why File?: Due to an ongoing assessment freeze, your assessed value may not reflect your property's true current market value, potentially causing you to overpay.
Cost: Free to file on your own if you know the real estate market well, or pay Ownwell a 25% fee on tax bill savings!
What Is a Nassau County Tax Grievance?
A tax grievance, also known as a property tax appeal or protest, is the process of disputing a property’s assessed value (not your tax rate) with the Nassau County Assessment Review Commission (ARC).
Typically, people file tax grievances when they believe or have proof that the Nassau County Department of Assessment inflated their property’s value.
A successful grievance ensures your property or properties are valued accurately, so you don’t overpay taxes. And with Nassau County’s history of reassessment freezes, filing for a tax grievance is even more important.
Nassau County is supposed to reassess property values every year before calculating each owner’s annual tax bill. But the county froze reassessments starting in the 2021–2022 tax year. In other words, assessed values haven’t changed for the past four years. And the freeze is expected to continue through 2025 and 2026.
That means if your property gains value during the freeze, you’ll be undertaxed. But if it loses value (or was overvalued before the freeze), you pay more than you should, unless you file for a tax grievance.
Who Is Eligible To File a Grievance in Nassau County?
Anyone who pays property taxes in Nassau County can file a tax grievance, whether you’ve owned your home or property for multiple years or just bought it recently. You can still file a grievance even if you don’t think your property is over-assessed.
Additionally, you’re not limited to filing just once. If you think the county’s assessment is wrong or unfair, you can challenge it each year.
What Are the Benefits of a Successful Tax Grievance?
Filing a Nassau County, NY, tax grievance comes with plenty of benefits if your application is approved:
Lower assessed value: When a grievance reduces your property’s assessed value, you pay less property taxes.
Long-term tax savings: You can keep saving money on taxes year after year if your property’s lowered assessed value remains the same over time. Enrolling in the New York STAR credit program can further increase your savings.
Locked-in reductions: Once the ARC lowers your property’s assessed value, that reduction stays in place until the next reassessment.
Tax Grievance Filing Timelines in Nassau County
On the first business day in January of every year, the Nassau County Department of Assessment publishes the tentative assessment roll — a list of properties in the county and their assessed values.
To contest your property’s assessment in the roll, you must file a Nassau property tax grievance between the publication of the tentative roll in early January and the statutory deadline of March 1st. However, the filing deadline can change, and the county has pushed it back a month over the past several years.
In 2025, for example, the deadline for filing a Nassau County property tax grievance for the 2026-2027 tax year was initially January 2 through March 3. But the county extended the deadline to April 1.
2026 Nassau County Tax Grievance and Payment Deadlines
In 2026, the Nassau County Department of Assessment will release a tentative assessment roll on January 2. The assessed values in the list will determine property taxes for the 2027-2028 tax year.
To contest your property’s assessment in the roll, you must file a Nassau property tax grievance between January 2, 2026, and March 2, 2026. Check the county’s official website regularly to make sure you don’t miss any deadline changes. If you miss the deadline, you can’t ask for an extension.
Grievance Process Step or Payment Date | Corresponding Date / Deadline |
|---|---|
Letter of Authorization Opens | September 4, 2025 |
Tentative Assessment Roll Published | January 2, 2026 |
Grievance Filing Deadline | March 2, 2026 (Statutory deadline; check for extensions) |
Final Assessment Roll Published | April 1, 2026 |
ARC Decision Date and Notification | By March 31, 2027 |
SCAR Appeal Filing Deadline | Within 30 days of the ARC decision notice |
First Half School Tax Payment Due | November 10, 2026 |
Second Half School Tax Payment Due | May 10, 2027 |
First Half General Tax Payment Due | February 10, 2027 |
Second Half General Tax Payment Due | August 10, 2027 |
How To File a Nassau County Tax Grievance
Want to reduce your Nassau County property taxes? Here’s how to file a grievance step by step:
Gather all relevant evidence: Anything that shows the county assessed your property for more than its worth can help your case. For example, if recent sales or appraisals of similar homes in your neighborhood are lower than your property’s assessed value, you can use them to show your assessment is too high.
Complete the tax grievance application form: You can fill and submit the RP-524 form online, ask ARC to mail one to your address by calling 516-571-3214, or complete a form in person at 240 Old Country Road, 5th Floor, Mineola, NY 11501.
Attach your evidence: When filing electronically, the county’s online appeal system allows you to attach all documents relevant to your tax grievance. You can also mail or submit them in person.
Filing a property tax appeal on your own is free in Nassau County. But it can take time and effort. If the tax grievance process feels time-consuming or overwhelming, our expert team at Ownwell can handle everything for you from start to finish.
What Evidence Is Needed To Support a Grievance?
Here are some of the most effective pieces of evidence in a property tax grievance in Nassau County, NY:
Recent sales of similar homes in your area show what comparable properties actually sold for. Prices lower than your assessed value are evidence that your property is overvalued.
Professional appraisals provide an expert opinion of your property’s market value.
Nassau County assessment records compare your property’s value with similar ones in the same area. If your property’s assessed value is higher, the county over-assessed it.
Property condition documentation, such as photos of major damage, can substantiate the necessity to lower your property’s assessed value.
What Happens After You File a Tax Grievance?
After you file a Nassau County tax grievance, the ARC reviews your application to decide if your property’s assessed value is too high. They can either reduce it or leave it as is. Your property's value cannot increase from filing a tax grievance.
The ARC will notify you of the final decision between the filing date and March 31 of the following year. For example, if you filed in February 2025, ARC has until March 31, 2026, to issue a decision.
If ARC offers a property assessment reduction, you can accept or reject it. If you disagree with the decision, you can file an appeal called Small Claims Assessment Review (SCAR) at the Nassau County Clerk’s office. However, the filing fee is $30, which you’ll get back if your appeal succeeds.
A representative like Ownwell covers the $30 SCAR fee (unlike many competitors) and only charges you for the service if you win your grievance.
Common Myths About Nassau County Tax Grievances
Some of the biggest myths about tax appeals in the county include:
A tax grievance is a lawsuit. No. It's just a simple property value appeal.
If you file an appeal, your taxes will go up. False. The ARC can only reduce or leave tax assessments unchanged.
You must show up in person for the appeal. Not true. You can complete the tax grievance online, by mail, or even through a third-party representative.
Everyone gets denied anyway. Wrong. About 80% of Nassau County homeowners who filed for tax grievances in 2024 got a reduction.
Filing a grievance can negatively impact your property market value. Absolutely not. It only lowers what the county uses to calculate your taxes, not what buyers would pay for the property.
Take the Next Step Before the Grievance Deadline Hits
With Ownwell as your representative, you’ll never miss out on the tax savings that come with filing a grievance. We help you appeal your property’s assessed value on time in Nassau County and meet New York property tax grievances deadlines in other counties.
The window for filing a Nassau County tax grievance for 2025 was between January 2 and April 1 (extended from March 3). Don’t miss future deadlines.
File your property tax grievance with Ownwell and save money! On average, we save Nassau County residents $1,538.
