Key Takeaways
Filing a grievance in Nassau County carries zero risk. The Assessment Review Commission (ARC) cannot raise your assessment.
62% of Long Island homeowners have already filed a grievance, nearly triple the national rate.
The filing window runs from January through March each year through ARC.
A $650,000 Nassau County home assessed 15% over market value could save roughly $2,050 annually.
Ownwell handles the entire grievance process on contingency. You pay nothing unless your taxes go down.
Table of Contents
If your Nassau County tax bill made you do a double-take this year, you're not alone. Property taxes on Long Island rank among the highest in the nation, and the county's assessment process routinely overvalues homes by 10% to 20%.
The good news: You can challenge that number. The even better news: There's zero risk in doing so.
This guide walks you through the Nassau County grievance process, shows you how much you could save with real dollar figures, and explains why homeowners who file with Ownwell save an average of $1,538 per year in Nassau County.
Whether you file on your own or work with a professional, the information here will help you make a confident, informed decision before the March deadline closes.
Why Most Nassau County Homeowners Should File a Grievance
Nassau County assesses over 423,000 properties valued at a combined $264 billion. At that scale, overassessments aren't the exception; they're a built-in feature of the system.
Here's what makes filing a grievance a clear financial decision: The Assessment Review Commission (ARC) cannot increase your assessed value as a result of your filing. If your grievance is denied, your assessment stays exactly where it was. You have nothing to lose.
Our Long Island survey of homeowners found that 62% of Long Island homeowners have filed a property tax grievance at least once, nearly triple the national rate of 22%. Long Island homeowners understand that the system rewards those who challenge it.
Our survey found something even more striking: 93% of Long Island homeowners agree the current system negatively affects those who don't file. In other words, staying silent effectively means subsidizing your neighbors who do file.
The real risk isn't filing a grievance. It's not filing one. Every year you skip is another year you may be paying thousands more than your home's market value justifies.
With Nassau County's 2.10% median effective tax rate, even a modest 10% reduction in assessed value on a $650,000 home saves you over $1,300 annually. Those savings compound year after year.
Consider what that means over a typical homeownership timeline. Five years of compounded savings from a single successful grievance can total $6,000 to $10,000, depending on the reduction. That's money you keep without changing anything about your home or your lifestyle.
How Much Are You Over Paying?
What Is a Property Tax Grievance in Nassau County?
A property tax grievance is a formal challenge to your home's assessed value. In Nassau County, you file this challenge with the Assessment Review Commission (ARC), the agency responsible for reviewing assessment disputes.
Nassau's process is distinct from the rest of New York State. While most counties use a local Board of Assessment Review, and New York City uses the Tax Commission, Nassau County routes all residential grievances through ARC. This process is grounded in New York Real Property Tax Law Section 524.
Understanding this distinction matters because the forms, deadlines, and procedures differ from what you'll find in generic state-level guides. If you follow instructions meant for Suffolk or Westchester County, you could miss the correct filing window or submit to the wrong agency.
Your assessed value is the county's estimate of your home's value. The county multiplies that number by the local tax rate to calculate your annual bill. When the assessed value is higher than your home's actual market value, you're paying taxes on money that doesn't exist.
Nassau County assesses over 423,000 properties valued at $264 billion, making its assessment roll one of the top 50 largest rolls in the country. With that volume, the county simply cannot evaluate every home with precision. That's exactly why the grievance process exists.
How to File a Property Tax Grievance in Nassau County
Filing a grievance in Nassau County follows a structured process. After processing over a million property tax challenges nationwide, we've found that preparation is what separates successful filings from unsuccessful ones. Here are the steps:
Check your assessment on the tentative roll: Nassau County publishes the tentative assessment roll each January. Review your property's assessed value and compare it to recent sales of similar homes in your neighborhood. If the assessed value exceeds what your home would realistically sell for, you likely have grounds to file.
Gather your evidence: The strongest grievance filings rely on three to five comparable sales within a half-mile radius, sold within the last 12 months. After reviewing hundreds of thousands of cases, we've found that recent, nearby comps carry the most weight with ARC reviewers. Include documentation of any condition issues, such as structural damage, outdated systems, or needed repairs. An independent appraisal strengthens your case but isn't required.
Complete Form RP-524 or file online: This is the official grievance application for Nassau County. You'll need your property's section, block, and lot number, your current assessed value, and the value you believe is correct, supported by your comparable sales data.
File with ARC before the March deadline: The filing window opens in January and closes in March. The past two years, the county has extended it by 3-4 weeks. However, missing this deadline means waiting another full year to challenge your assessment, so mark it on your calendar early.
Attend your hearing or submit evidence by mail: ARC will schedule a hearing where you can present your case in person. You can also submit your evidence package by mail if you prefer not to attend. Either way, organized and well-documented evidence makes the difference.
Receive your determination: The ARC will notify you of its decision. If your grievance is granted, your assessed value drops and your tax bill adjusts accordingly. If denied, you can escalate to Small Claims Assessment Review (SCAR) or pursue a formal Article 7 proceeding in court.
Many homeowners never make it to step one. Among Long Island homeowners who have never filed a grievance, 35% didn't know they had the right, 43% assumed they wouldn't qualify, and 16% found the process too confusing.
None of those barriers is a real disqualifier. If your home's assessed value exceeds its market value, you qualify. The process is straightforward, and you can file it yourself or have a professional handle it.
One important timing note: if your Notice of Assessed Value arrived this month, your filing window is already open. Every day you wait is a day less to gather comparable sales and build your case. Don't let the March deadline pass without taking action.
For a deeper look at the full grievance process, including evidence strategies and hearing preparation, see our Nassau County property tax grievance guide.
How Much Can You Save? A Nassau County Example
The best way to understand the value of filing a grievance is to see the math. Here's a worked example using a typical Nassau County home valued at $650,000, which falls squarely in the typical Long Island price range.
The formula is simple: assessed value multiplied by the effective tax rate equals your annual tax bill. When your assessed value drops, your bill drops by the same proportion.
Scenario 1: 15% Reduction
Before Grievance | After Grievance | |
|---|---|---|
Assessed value | $650,000 | $552,500 |
Effective tax rate | 2.10% | 2.10% |
Annual tax bill | $13,650 | $11,603 |
Annual savings | $2,048 |
That $2,048 in annual savings is enough to cover two months of utility bills or a year of home insurance premiums.
Scenario 2: 10% Reduction
Before Grievance | After Grievance | |
|---|---|---|
Assessed value | $650,000 | $585,000 |
Effective tax rate | 2.10% | 2.10% |
Annual tax bill | $13,650 | $12,285 |
Annual savings | $1,365 |
Even the more conservative 10% scenario puts over $1,300 back in your pocket each year.
Keep in mind that a successful grievance doesn't just save you money in year one. Your reduced assessment becomes the new baseline for future tax calculations.
This isn't hypothetical money. 76% of U.S. homeowners say property taxes exceeded their budget last year, up 10 percentage points from the prior year.
If your tax bill feels unsustainable, a grievance is the most direct path to relief.
DIY vs. Hiring a Professional: What to Consider
You have two options for filing a grievance: handle it yourself or hire a professional. Both can work, but they involve different tradeoffs.
Filing on your own gives you full control and costs nothing. You'll need to research comparable sales, complete Form RP-524, and either attend an ARC hearing or submit your evidence by mail.
Hiring a professional means someone experienced with the ARC process handles the research, paperwork, and hearings on your behalf. Firms, like Ownwell, that work on a contingency charge nothing upfront, and you only pay if your taxes are reduced.
Here's how the two options compare:
Factor | DIY | Professional |
|---|---|---|
Cost | Free | Contingency fee (typically 25% of first-year savings) |
Time investment | 5-10 hours for research, filing, and hearing | Minimal, usually under 10 minutes to sign up |
Evidence quality | Depends on your research skills | Built from professional comp databases and local market expertise |
Success likelihood | Varies widely | Higher, based on experience with ARC procedures |
Escalation to SCAR | You handle it yourself | Included in the service |
74% of U.S. homeowners have never challenged their tax bill. Among them, 57% didn't know they could. If you're in that group, the DIY route can feel overwhelming before you even start.
The contingency fee model removes the financial risk from hiring a professional. You pay nothing unless your taxes actually decrease. If the grievance doesn't result in savings, you owe nothing.
For homeowners who value their time or aren't confident in their ability to identify strong comparable sales, the professional route often delivers a better outcome for less effort.
Traditional tax reduction firms on Long Island have served Nassau County homeowners for decades. However, many charge flat fees or require multi-year contracts. Ownwell's contingency model aligns your interests: we only succeed when you do.
For more on how Nassau County property tax reduction works and what to expect from the process, see our detailed breakdown.
How Ownwell Can Help With Your Nassau County Grievance
Ownwell manages the entire Nassau County property tax grievance process from start to finish. We analyze your assessment, build an evidence package with comparable sales and market data, file with ARC on your behalf, and attend hearings when needed.
You start by entering your address. In about 15 seconds, you'll see a free savings estimate based on your property's current assessment and local market data. If the numbers look right, you sign up, and we take it from there.
Our pricing is straightforward: Ownwell's 25% contingency fee means you pay 25% of your first-year savings. If we don't reduce your taxes, you pay nothing. That's our Savings-Or-Free Guarantee.
The numbers speak for themselves:
88% success rate across all property tax challenges in 2025
4.7-star rating across 3,000+ Google reviews
Processed over one million property tax challenges nationwide
If ARC denies your grievance, we don't stop there. Ownwell can escalate your case to SCAR on your behalf, giving you a second opportunity for a reduction without additional effort on your part.
Ready to see what you could save? Get your free savings estimate in about 15 seconds. Just enter your address.
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Frequently Asked Questions
Can Nassau County Raise My Assessment if I File a Grievance?
No. The Assessment Review Commission cannot increase your assessed value as a result of a grievance filing. If your grievance is denied, your assessment stays exactly the same. Filing is completely risk-free.
What Is the Deadline to File a Property Tax Grievance in Nassau County?
The filing window opens in January when the tentative assessment roll is published and closes in March. The exact deadline varies each year slightly, so check ARC's website or your Nassau County property tax details for the current year's date.
What Evidence Do I Need to File a Grievance?
The strongest filings include three to five comparable sales of similar homes nearby, sold within the last 12 months. Documentation of property condition issues and an independent appraisal also help, though an appraisal isn't required. You'll file your evidence with Form RP-524.
How Long Does the Nassau County Grievance Process Take?
Most grievances filed with ARC are resolved within three to six months of the filing deadline. If you escalate to SCAR, the timeline extends further, sometimes up to an additional year. Ownwell handles all follow-up and timeline tracking on your behalf.
What Happens if My Grievance Is Denied?
You have two escalation options. You can file with the Small Claims Assessment Review (SCAR) for an independent review, or pursue a formal Article 7 proceeding in New York State Supreme Court. SCAR is the more common and accessible route for residential homeowners. Ownwell can handle your SCAR escalation as part of the grievance service.
