How to File a Long Island Tax Grievance and Lower Your Tax Bill

Key Takeaways

• Nassau County's grievance window opens every January and is due in early March (sometimes extended). Suffolk's Grievance Day is the third Tuesday in May. Always confirm the current deadline at the Ownwell Nassau County grievance filing page before filing.

• Nassau uses Form AR1 with the Assessment Review Commission (ARC); Suffolk uses Form RP-524 with your town's Board of Assessment Review.

• Filing a grievance cannot increase your assessment; it can only stay the same or go down under New York Real Property Tax Law §525.

• Our Nassau County customers saved an average of $1,462 with a 93% success rate on grievances.

Introduction

Long Island homeowners carry some of the highest annual tax burdens in the country. Nassau County's median annual tax bill is $3,634 — well above the national median. Filing a Long Island property tax grievance is the most direct path to reducing what you owe. Our Long Island Homeowner Property Tax Survey found that 62% of Nassau and Suffolk County homeowners have filed a grievance, nearly triple the national rate.

Most homeowners who grieve win reductions that last for years. We handle the entire process — paperwork, evidence, hearings — so you don't navigate it alone.

This guide covers everything you need: filing deadlines, required forms, evidence requirements, and what to expect at each step. For a county-specific walkthrough, see Ownwell's Nassau County tax grievance guide.

What Is a Tax Grievance?

A tax grievance is a formal request to ask your county to lower your property's assessed value. In New York, this process is called a "grievance."

Here's how assessed value connects to your tax bill:

Assessed Value × Tax Rate = Annual Tax Bill

*Nassau County assesses property at a fraction of market value. These figures use Nassau County's 1.55% median effective rate and median annual tax bill of $3,634 on a median home value of $518,000. A 15% reduction in assessed value saves roughly $551 per year. A grievance challenges your assessed value, not the tax rate itself.

You can grieve your assessment if you believe the county has overvalued your property compared to recent sales of similar homes, or if your property has condition issues that reduce its market value.

Why You Can Challenge Your Assessment: Four Legal Grounds

New York law gives every property owner the right to challenge their assessment under Real Property Tax Law (RPTL) §524. Four legal grounds support a grievance:

1. Excessive assessment: The county has valued your property above its true market value — the most common ground for Long Island homeowners. Supporting evidence includes recent comparable sales.

2. Unequal assessment: Your home is assessed at a higher percentage of market value than similar properties in your area, even if the dollar figure seems accurate.

3. Unlawful assessment: The assessment violates a specific legal provision — for example, a tax-exempt property was assessed, or the wrong authority assessed it.

4. Misclassification: Your property is placed in the wrong tax class. A mixed-use property that is primarily residential but classified as commercial is a common example.

Most Long Island homeowners file on the grounds of excessive or unequal assessment. The evidence requirement is the same in both cases: recent comparable sales of similar homes that sold for less than your assessed value.

When Are Long Island Grievance Deadlines?

Nassau and Suffolk Counties run on different annual timelines and use different processes. If you missed this year's window, now is the time to prepare for next year, so you don't wait another full cycle to file.

• Nassau County: For 2027, the statutory grievance window opens January 4 and closes on March 2, with extensions in recent years. Confirm the current deadline and authorize your filing at Ownwell Nassau County grievance filing.

• Suffolk County: Grievance Day is the third Tuesday in May. Each of the ten Suffolk towns has its own Board of Assessment Review, so file with the assessor's office in the town where your property is located.

For a snapshot of local rates as you prepare, review the latest Ownwell's Suffolk County property tax trends.

Nassau County vs. Suffolk County: Key Process Differences

Understanding which process applies to your property saves time and prevents rejected filings.

What's SCAR? Small Claims Assessment Review (SCAR) is a simplified court proceeding for residential homeowners who want further review after an unfavorable ARC or BAR decision.

The filing fee is $30, and you must file within 30 days of receiving your decision. Commercial properties use a separate judicial process called tax certiorari.

Six Steps to File Your Long Island Grievance

Whether you're in Nassau or Suffolk County, the grievance process follows a similar structure. The forms and filing bodies differ, but the evidence and strategy remain the same.

Step 1: Check Your Current Assessment

Start by looking up your property's assessed value:

• Nassau: Use the Nassau County ARC website property search

• Suffolk: Visit your town assessor's website via the Suffolk County Real Property Tax Service Agency

Verify that the property details (lot size, square footage, number of bedrooms) are accurate. Even small errors can inflate your assessed value. In our Nassau County filings, misrecorded bedroom counts and lot-size discrepancies are among the most common assessment errors we identify — and they're among the easiest to correct.

Step 2: Research Comparable Sales

The strongest grievances include three to five comparable sales ("comps") of similar homes that sold recently for less than your assessed value. Look for properties that match your home's:

• Square footage (within 10-15%)

• Lot size

• Number of bedrooms and bathrooms

• Age and condition

• Neighborhood

Nassau's Land Records Viewer provides recent comparable sales by neighborhood, lot size, and property class. After processing grievances for thousands of Nassau and Suffolk homeowners, we've found the difference between winning and losing usually comes down to three to five well-chosen comps that clearly show the assessed value is higher than market value.

Step 3: Document Property Condition Issues

Physical problems that reduce market value strengthen your case. Document issues such as:

• Foundation or structural damage

• Outdated electrical or plumbing systems

• Roof damage or age

• Water damage or flooding history

• Environmental concerns (near a busy road, power lines)

Photos, repair estimates, and inspection reports provide concrete evidence the county can't easily dismiss. In our experience, repair estimates from licensed contractors carry the most weight with Nassau's ARC — boards respond to documented costs, not general condition descriptions.

Step 4: Complete the Correct Form

• Nassau County: File Form AR1 online through AROW. You'll need your property's Section-Block-Lot number, the assessed value you're requesting, and supporting documentation. The most common filing mistake is omitting the correct Section-Block-Lot — double-check it against your tax bill before submitting.

• Suffolk County: File Form RP-524 with your town's Board of Assessment Review. Include comparable sales data and any evidence of condition issues.

• Village properties: If your property is in an incorporated village, villages maintain their own assessment rolls and may set separate BAR filing deadlines — confirm with your village assessor's office.

Step 5: Submit Before the Deadline

File early to avoid last-minute technical issues:

• Nassau: By the early-March deadline (extensions sometimes occur — confirm at Ownwell Nassau County grievance filing), via AROW

• Suffolk: By Grievance Day, the third Tuesday in May, to your town assessor's office

Keep copies of everything you submit. If filing by mail in Suffolk, use certified mail to confirm receipt. Filing early — at least two weeks before the deadline — also gives you time to correct any missing attachments without missing the window.

Step 6: Attend Your Hearing (If Required)

In Nassau, ARC may schedule an informal conference to discuss settlement. In Suffolk, you may receive a denial letter with instructions to file SCAR if you want to continue.

Most grievances in Suffolk are initially denied at the town level, with resolution coming later through SCAR. This isn't a rejection of your case; it's standard procedure given the volume of filings and short review window.

Skip the research — let Ownwell build your case.

How Long Does the Grievance Process Take?

The Nassau County grievance cycle is longer than most homeowners expect:

• ARC filing window: January through early March; ARC typically issues decisions before year-end. If approved, savings appear on your October school tax bill and January general tax bill.

• SCAR (if needed): File within 30 days of the ARC decision; hearings typically resolve within 6-12 months after filing.

• Total timeline: 12-24 months from filing to final resolution, depending on whether SCAR is needed.

In Suffolk County, Board of Assessment Review decisions usually come within 30-60 days of Grievance Day. If SCAR is needed, add 6-12 months.

Any reduction is retroactive to the tax year you filed — you won't lose credit for the months the case was pending.

Can Filing a Grievance Raise My Taxes?

No. Under New York Real Property Tax Law §525, filing a grievance cannot result in a higher assessment. Your assessed value can only stay the same or go down.

This makes grieving a low-risk opportunity. Even if your grievance is denied, you're no worse off than before you filed.

How Often Should You File a Grievance?

File every year. Assessments can increase annually, and a reduction won in one year doesn't guarantee the same value the next. Many Long Island homeowners file routinely to prevent their assessments from creeping back up.

You can only grieve the current assessment year; you cannot go back and challenge previous years' assessments. You may still claim exemptions you missed — we can help apply for retroactive exemptions in New York.

Nassau's filing window generally opens in January each year. You can authorize Ownwell to file your Nassau County grievance before the window opens, so you're ready when it does.

Exemptions vs. Grievances: What's the Difference?

Grievances and property tax exemptions are separate paths to lower taxes, and you can pursue both.

In New York, the Basic STAR Exemption is available to owner-occupied primary residences. If you qualify for exemptions you haven't claimed, you may be leaving money on the table on top of any grievance savings.

How Ownwell Can Help

We handle Long Island grievances end to end: gathering comps, preparing evidence, filing forms, and attending hearings on your behalf.

Ownwell's 2026 Nassau County customers saved an average of $1,462 per year with a 93% success rate, and we maintain a 4.7-star rating across 3,000+ Google reviews. Our Nassau County Grievance Study documents these results across thousands of ARC filings (ARC-level grievances only, not SCAR outcomes).

See what we can do for Ownwell Nassau County property tax reduction.

Our pricing is simple: Ownwell's 25% contingency pricing. If we don't reduce your assessment, you pay nothing. No upfront costs, no risk.