Nassau County, NY Property Tax Grievance: How It Works in 2026

Nassau is the only downstate county where the county itself values homes. The Nassau County Department of Assessment sets values for roughly 385,000 parcels, so your challenge goes to the county, not your town.

Specifically, it goes to the Assessment Review Commission, usually called ARC. Everywhere else in New York outside New York City, towns and cities do the assessing and you would file a Form RP-524 with a local board instead. Nassau runs its own track with its own form.

One more thing that makes Nassau unusual right now: the assessment roll has been frozen since the 2021-22 tax year, through the 2026-27 tentative roll. A frozen roll in a market that has kept moving means errors and inequities grow over time, which strengthens many grievance cases.

For context, ATTOM's 2025 data put New York's average single-family tax bill at $7,732, the fifth highest of any state. Nassau homeowners typically pay well above even that statewide average.

The window opens when the tentative roll is published on January 2 and normally runs through March 2. For the 2026 cycle, which covers the 2027-28 tax year, the county extended the deadline to March 31, 2026.

That window has now closed, so the next opportunity opens January 2, 2027. Your application must be received by the deadline. A postmark does not count.

The window comes around every year, so the smart move this summer and fall is to gather your evidence early: recent sales of similar homes, photos of any condition problems, and your latest assessment notice.

Homeowners who win are usually the ones whose comparable sales are pulled together before the roll comes out, not the ones scrambling in the final week of the window.

The process is simpler than most homeowners expect, and filing costs nothing. Every deadline is received-by rather than postmark, so build in a buffer if you file anything on paper.

Here is the sequence once the window opens.

Nassau assesses Class 1 residential homes at a tiny fraction of market value, around 0.1 percent since the 2020-21 reassessment. That means a $500,000 home shows an assessed value near $500, and the tiny number on your notice is not your market value.

Divide your assessed value by the level of assessment shown on your notice to get your implied market value. If that number is higher than what your home would realistically sell for, you have a case.

Because the roll has been frozen since 2021-22, the county's value may reflect a market that no longer exists on your street. Sales from the past year are the cleanest way to show what has actually changed.

The strongest supporting evidence includes:

ARC reviews grievances filed during the window and can settle directly with homeowners, so a well-documented case often ends in a reduction offer without any hearing.

If ARC denies your grievance or you turn down the offer, the next step is Small Claims Assessment Review, known as SCAR. It costs $30, runs like an informal small claims hearing, and is limited to owner-occupied one, two, and three family homes.

If you filed in the 2026 window and were denied, ask ARC about the SCAR petition deadline for your case. That $30 petition is the remaining live option this year.

Whatever happens, your assessment cannot go up because you filed. ARC states it will never increase an assessment as a result of a grievance.

Nassau's typical tax bill is among the highest in the country. The median bill exceeds $10,000, the Census actually top-codes Nassau at $10,000 and up, and effective tax rates are commonly cited around 1.8 to 2.1 percent on a median home value of roughly $650,000.

Run the math on a $650,000 home at about 2 percent and you get a bill near $13,000 a year. A 10 percent assessment reduction saves about $1,300 a year, and that saving repeats every year the lower value holds.

For comparison, the average US single-family bill in 2025 was $4,427 at an average effective rate of 0.90 percent. Nassau homeowners pay roughly three times the national average, which is why even a modest reduction is meaningful.

One clarification: STAR, the school tax relief benefit for owner-occupied primary residences, is completely separate from grieving and is unaffected by it. Exemptions lower your bill one way and a grievance lowers it another, so pursuing one does not cost you the other.

Most of your neighbors have already decided it is. A majority of Nassau homeowners grieve their assessment every year, and most homeowners who challenge win reductions, according to local reporting.

There is essentially no downside. Filing with ARC is free, the worst realistic outcome is that your value stays the same, and a win keeps saving you money year after year.

The main cost is time: pulling comparable sales, doing the ratio math, filing, and following up through SCAR if needed. A service like Homespring handles that entire process for you with no upfront fee, which is worth considering before the window opens on January 2, 2027.