How to Appeal Property Taxes in Nassau County, New York (2026 Guide)

The 2026 Nassau County appeal window for the 2027/28 assessment roll opened January 2, 2026; ARC’s regular published deadline was March 2, 2026, and the official 2027/28 brochure says the filing deadline was extended to March 31, 2026. As of July 2026, that window is closed; the next regular ARC deadline should be Monday, March 1, 2027, because ARC’s rule runs from the first business day in January through the first business day in March.

File with the Nassau County Assessment Review Commission (ARC), not the Assessor: online through AROW—Assessment Review on the Web, or by mail/hand delivery to Assessment Review Commission, 240 Old Country Road, 5th Floor, Mineola, NY 11501. ARC charges no filing fee.

How assessments work in Nassau County

Nassau reassesses annually. The Department of Assessment publishes a tentative roll at the start of January, and that roll becomes final on April 1 of the following year. The January 2, 2026 tentative roll is the 2027/28 assessment: it affects the October 2027 school tax bill and the January 2028 general tax bill. The county calendar says ARC reviews 2027/28 appeals from March 3, 2026 through March 31, 2027, the final roll is published April 1, 2027, and the court-review deadline is April 30, 2027.

For most homeowners, the key numbers are full market value, level of assessment, and assessed value. Nassau’s 2027/28 tentative notices state that Class 1 homes use a 0.1% level of assessment: a $700,000 market value equals a tentative assessed value of 700. Class 1 generally means one-, two-, and three-family homes and certain Class 1 condos. Class 1 assessment increases, excluding new construction or renovation, are capped at 6% in one year and 20% over five years.

Nassau tax rates are not one countywide number. Your bill combines school district, town/city, county and special district rates, and villages may maintain separate assessments for village taxes. That is why a reduction of 50 assessed-value points saves different dollars in Plainedge than in Manhasset.

Whether you should appeal

Appeal if Nassau’s market value is higher than what your home would likely have sold for on the valuation date, or if the county has wrong facts: living area, lot size, finished basement, condition, classification, or missing exemptions. Start with the county Land Records Viewer / My Nassau Property page. Compare your tentative market value with recent sales of similar nearby homes, not with list prices or Zillow estimates alone.

A simple Class 1 test: because Nassau uses 0.1%, divide the tentative assessed value by 0.001 to see the market value behind it. If your tentative assessed value is 850, Nassau is effectively valuing the home at about $850,000. If strong comparable sales support $775,000, your requested assessed value would be about 775.

Do not rely on countywide “success rate” claims from tax-reduction firms. I found no current official Nassau publication giving a 2026 residential ARC success rate or median reduction. ARC’s AROW system does let users query public information on past and pending assessment appeals, which is useful for parcel-level research, but that is not the same as a countywide published success statistic.

Also check exemptions before or alongside an appeal. Nassau’s Department of Assessment lists Senior Citizens, Persons with Disabilities and Limited Incomes, Basic/Enhanced STAR, Alternative Veterans, Cold War Veterans, Eligible Funds, volunteer firefighter/ambulance worker, clergy, home improvement, and accessibility-related improvement exemptions. For 2027/28 exemption applications, the county’s HELP calendar says applications must be received by January 4, 2027. STAR is state-administered for new applicants.

Step-by-step how to file

1. Look up your January tentative assessment. Use your Section/Block/Lot, address, or the notice from the Department of Assessment. Check the 2027/28 column if you are reviewing the January 2, 2026 roll.

2. Choose the right ARC form. ARC’s official forms are:

   • Form AR1 — Application for Correction of Property Tax Assessment for valuation claims on an exclusively residential one-, two-, or three-family home or Class 1 condo.
   • Form AR2 — Application for Correction of Property Tax Assessment for valuation claims on other property types.
   • Form AR3 — Application for Correction of Property Tax Assessment for Claims Other Than, or in Addition to Valuation, Including Misclassification or Denial of Exemption.
   • Form AR10 if someone else represents an individual taxpayer.
   • Form AR12 to withdraw paper applications.

3. State your requested value carefully. For a Class 1 house, convert your evidence to an assessed value using the applicable level of assessment. If you think a $700,000 tentative value should be $640,000, your requested assessed value is about 640. You generally should not ask for less than you can support.

4. Attach proof. Best evidence is recent comparable sales, an appraisal, closing statement if you bought recently, photos showing condition problems, permit/CO facts, or corrected inventory information. For AR3 exemption appeals, ARC says its review is appellate only: it cannot consider documents that were not already submitted to the Department of Assessment before that department made its exemption determination.

5. File by an allowed method. Online filing through AROW is recommended by ARC and gives you an appeal number, email confirmation, status tracking, and electronic notices. Paper applications may be mailed or hand-delivered to Assessment Review Commission, 240 Old Country Road, 5th Floor, Mineola, NY 11501. Mail must be postmarked by the deadline. In-person filing is during weekday office hours, generally 9:00 a.m.–4:30 p.m. ARC lists email addresses for questions and representative registration, but the official filing page describes filing by online portal, mail, and in person—not ordinary email filing.

What happens after

ARC is an independent county agency, separate from the Department of Assessment. It reviews timely applications and may reduce an assessment, change classification, or address an exemption issue; it cannot increase your assessment.

Most homeowner appeals are not courtroom-style trials. ARC’s rules say the process is meant to be speedy and inexpensive, and formal court evidence rules do not apply. A reviewer—an ARC commissioner or employee designated by the chairperson—reviews the application. If you filed a complete application and complied with information requests, you may request a conference to present argument or oral testimony; conferences may be by telephone if ARC agrees. Otherwise, many cases are decided on the written submission, and ARC may send an offer of reduction or preliminary determination through AROW or by notice.

Expect a long timeline. ARC’s FAQ says review can take up to 15 months, with final determinations issued by March 31 of the year after filing. For a 2027/28 appeal filed in 2026, look for final action by March 31, 2027 and the final assessment roll on April 1, 2027. If you disagree with ARC’s final result, eligible owner-occupants may file Small Claims Assessment Review (SCAR); the state court system describes SCAR as an informal review before a trained hearing officer with a $30 filing fee. Nassau’s calendar lists April 30, 2027 as the 2027/28 judicial-review deadline.

Local tips

• File every year you disagree. Nassau’s process overlaps: you may still be waiting on last year’s ARC decision when the next January tentative roll appears. ARC says each year is a separate assessment.
• Avoid duplicate filings. If you signed an authorization for a tax representative, do not also file yourself unless you are sure no representative filing will be made. Duplicate applications can cause problems.
• Condos need coordination. A condo board may file for units; check with management first so the same unit is not duplicated.
• Use your actual tax bill for savings. A worked example using official state STAR data: New York lists Plainedge, Town of Oyster Bay, Class 1 Basic STAR maximum savings for 2026–2027 at $1,093, and the Nassau Class 1 Basic STAR exemption amount at 50 assessed-value points. That implies about $21.86 of school tax per assessed-value point in that segment. If a Plainedge Class 1 homeowner proves the market value should drop from $650,000 to $600,000, the assessment drops from 650 to 600, or 50 points. The school-tax savings alone would be about 50 × $21.86 = $1,093 for that year. General, county, town and special-district savings would be additional or different depending on the parcel, so use your actual bill for a precise estimate.
• Check exemptions before January 4, 2027. Missing STAR, senior, disability, veterans or volunteer-service exemptions can be worth as much as, or more than, a valuation appeal.