Your Nassau or Suffolk Property Tax Bill Might Be Wrong, Here Is How to Check
Every January a new round of Long Island homeowners finds out their assessment went up, and most never check whether they can push back.
Nassau and Suffolk run two completely different systems for challenging what the county says your home is worth. Get the timing wrong and you wait a full year for another shot. Get it right and any reduction you win follows you onto future tax bills.
How Nassau's window works
Nassau publishes a tentative assessment roll every January 2, and that single date starts the clock. The formal filing period runs from January 2 through the statutory March 1 deadline, though the county has pushed that date back in recent cycles. You file through the Assessment Review Commission, known as ARC, not your town, and the roll you are grieving in early 2026 becomes final more than a year later.
The filing itself goes through an online portal using Form AR-1. Miss the window and the county will not grant an extension on request. The next chance does not come until the following January.
Suffolk plays by different rules
Suffolk does not run a centralized commission. Instead each town holds its own Board of Assessment Review, and the statewide deadline for most of New York, Suffolk included, is Grievance Day, which falls in most communities on a set date each May. You file Form RP-524 directly with your town assessor or Board of Assessment Review rather than through a county office. That means ten separate filing offices across Suffolk's towns, each handling its own grievance day.
The filing window in Suffolk is short. The tentative roll typically publishes on May 1 and the deadline lands about two and a half weeks later, giving owners a narrow stretch to pull comparable sales and put together a filing. If you mail your form, state guidance is clear that it must actually be received by the assessor or board by Grievance Day, not just postmarked.
What a grievance can and cannot do
A grievance challenges your assessed value, the number the county uses to calculate your share of school, town, and county levies. It does not touch the tax rate itself, and it cannot lower your bill below what the math already allows. The upside is there is no real downside to trying: by law a Board of Assessment Review can only confirm or reduce your assessment, never raise it.
If your filing is denied at the local level in either county, the next stop is Small Claims Assessment Review, a court process available to most homeowners who want a second look at the decision.
Before you file anywhere, pull your property's current assessed value and compare it against recent sales of similar homes nearby. That comparison is the entire case. If the numbers do not match up, you have a reason to file. If they do, you have saved yourself the paperwork.
If you are weighing whether your assessment lines up with what your house would actually sell for, check your home value at /my-home-value/ or send me a question at /askmuds.