Nassau County uses the independent Assessment Review Commission, or ARC, to review applications for correction of assessment. The 2026 filing period concerned the 2027/28 tentative assessment placed on the roll January 2, 2026. Although ordinary materials referenced March 2, the county officially extended the closing date to March 31, 2026. That window is now closed. Homeowners could self-file without an attorney through Assessment Review on the Web, known as AROW, or use the county's paper process. FairPath can organize a manual future-cycle file containing the tentative assessment, county land records, sales, condition evidence, and official instructions; it does not claim a live 2026 filing or automated Nassau packet.
Assessment context: Nassau's assessment calendar is forward-looking: the tentative assessment challenged in early 2026 affects the October 2027 school tax bill and January 2028 general tax bill. Confirm the section, block and lot, tax class, tentative assessed value, exemptions, and Department of Assessment record. The county's Land Records Viewer provides roll data, tax maps, photographs, taxes, rates, exemptions, and comparable-sales tools, though automated access is constrained. ACS 2024 five-year data reports a $684,700 median owner-occupied value, taxes in the $10,000-and-over top category, and roughly 93 percent of housing built before 2000. These county measures show high burden and mature stock, but they do not determine a property's assessment or expected reduction.
Filing process: AROW is Nassau's free online self-filing service. It lets a registered owner search sales, submit an application, track its status, and receive electronic communications. ARC also accepts paper applications by mail or hand delivery at 240 Old Country Road, Fifth Floor, Mineola, subject to current instructions. The county says there is no fee to file with ARC and no attorney requirement for an owner filing personally. Keep the tentative-roll record, application, estimate of market value, selected sales, authorization if another person files, submission confirmation, and any proposed reduction or determination. ARC may take up to 15 months, and an owner may accept or decline a proposed reduction. A fresh assessment requires a fresh annual application.
Evidence to review: For a Nassau residential value review, begin with AROW's sale locator and the Land Records Viewer, then verify each candidate sale's date, section-block-lot, style, living area, age, lot, condition, and immediate location. Nassau's mostly pre-2000 housing stock makes renovation and effective age significant: a fully modernized property should not be treated as identical to an original-condition subject. Dated photographs, inspections, permits, repair estimates, floor plans, and corrected county facts can explain material differences. Tax class and exemption disputes require documents tailored to those issues rather than sales alone. Build an exhibit index that distinguishes market value, assessed value, class, exemptions, and tax impact. FairPath organizes the owner's selected sources but does not choose a claimed value or file with ARC.
Current deadline guidance: March 31, 2026 for the 2027/28 tentative assessment. Nassau County extended its 2026 ARC application period through March 31, 2026 for appeals of the 2027/28 tentative assessment set on January 2, 2026. That filing period is closed; the exact next-cycle deadline has not been confirmed here.
Nassau's tax-year labels can be confusing. The application filed in early 2026 addressed the 2027/28 tentative assessment and later school and general tax bills, so every saved document should identify the roll year it concerns.
AROW registration is required to file but not to use all public sale and inquiry functions. A homeowner can research before the filing period opens and then confirm that a completed application appears in the account.
Nassau separates ARC from the Department of Assessment. The Department sets the tentative roll; ARC reviews timely correction applications. Communications with one office should not be mistaken for a filing with the other.
The county's older housing, villages, school districts, and varied residential forms make countywide averages weak comparables. Favor local sales with matched property type and explain renovations, lot, location, and condition.
Official filing authority: Nassau County Assessment Review Commission. https://www.nassaucountyny.gov/arcwebcitizen/Jsp/HomePage.jsp
Source: Nassau County Government, Assessment Review Commission, https://www.nassaucountyny.gov/1510/Assessment-Review-Commission. Reviewed 2026-07-15.
Source: Nassau County Assessment Review Commission, Assessment Review on the Web, https://www.nassaucountyny.gov/arcwebcitizen/Jsp/HomePage.jsp. Reviewed 2026-07-15.
Source: Nassau County Government, How to Appeal Your Assessment, https://www.nassaucountyny.gov/2207/How-to-Appeal-Your-Assessment. Reviewed 2026-07-15.
Source: Nassau County Assessment Review Commission, ARC 2027-28 Filing Brochure, https://www.nassaucountyny.gov/DocumentCenter/View/51758/ARC-Trifold-2027-28-english-EXTENDED?bidId=. Reviewed 2026-07-15.