The Property Tax Grievance Window Works Differently in Nassau and Suffolk
*If you think your Long Island home is assessed too high, the calendar matters more than the paperwork.*
Every Long Island homeowner pays property tax based on an assessed value set by the county or town. If that number is wrong, you can challenge it. But Nassau and Suffolk run this process on completely different clocks, and missing the window means waiting another year no matter how strong your case is.
How Nassau County Handles It
In Nassau, the Assessment Review Commission reviews challenges to the assessed value the Department of Assessment puts on your home. The standard filing period runs from early January through March 1, and appeals are filed through the county's online system called AROW, or Assessment Review on the Web.
For the 2026-27 tax year, the filing period ran from January 2 through March 31, 2026, after the county extended what is normally a March 1 cutoff. Extensions have happened before, but nothing says one will happen again. If you want to grieve your assessment for next year's roll, plan to file by March 1 and treat any extension as a bonus, not a guarantee.
When you file, you are expected to bring evidence. The Town of North Hempstead advises homeowners to provide sales data for comparable homes in their neighborhood, and ARC has an online sales locator tool to help build that case.
Once the filing window closes, ARC reviews the applications and sends out determination letters. Under the 2026-27 calendar, ARC's review period ran into late March, with final determination letters going out around March 31 and the finished assessment roll published April 1. Homeowners who disagree with the outcome still have a further option: judicial review, with a filing deadline of April 30 for that same tax year.
How Suffolk County Is Different
Suffolk does not follow Nassau's calendar. Grievance day in Suffolk falls on the third Tuesday in May rather than the winter and early spring window Nassau uses, and the process runs through each town's individual Board of Assessment Review instead of one county commission. That means a Suffolk homeowner working off a Nassau neighbor's timeline could miss the entire window without realizing it.
Because Suffolk's assessments and grievance procedures run through the town assessor's office rather than a single county body, the exact forms and local contact points vary by town. If you own property in Suffolk, the safest move is to check with your specific town assessor early in the year rather than assume a single islandwide date applies.
What This Means If You Are Buying or Already Own
A grievance does not erase your tax bill. It only asks the county or town to confirm your assessed value is fair and in line with what similar homes nearby are actually worth. If you just bought a home, or if your assessment jumped after a reassessment year, this is the mechanism for pushing back, and it costs nothing to file yourself.
The practical risk is not filing on time. Nassau's window closes hard on its deadline each year, and Suffolk's town by town system means there is no single islandwide date to circle. If you are not sure whether your assessment looks right, comparing it to recent sales of similar homes nearby is the same first step either county expects you to take.
If you want a second opinion on how your assessment compares to what is actually selling nearby, drop a question at /askmuds or look up your home value at /my-home-value/.