Pull up two listings under "Larchmont, NY 10538." Same zip code, same post office, similar lot size, maybe a block apart. A buyer comparing them on price per square foot is missing the only fact that actually determines what each one will cost to own: whether the parcel sits inside the incorporated Village of Larchmont or in the unincorporated area of the Town of Mamaroneck next door. Those are two different governments, and the zip code doesn't tell you which one you're buying into.
This isn't a technicality that only matters to a village clerk. It decides which police department answers your call, which government hauls your trash, which elementary school you're zoned for, and how many separate tax bills land in your mailbox every year. And this year it decided something else: which side of that line is absorbing the steeper property tax increase, which is the opposite of what happened last year.
Where the line came from
The Village of Larchmont has only existed as its own municipality since 1891, when residents of what was then called Larchmont Manor petitioned the state legislature to incorporate. At the time, a New York town was legally limited to basic government functions, and Larchmont's growing population needed water supply, sewage disposal, garbage collection, and police protection that the Town of Mamaroneck couldn't provide on its own. So the Manor split off, and to meet a state minimum population density it had to expand beyond its original acreage. What's now the Town of Mamaroneck is really three pieces stitched together: the one-square-mile Village of Larchmont, a 5.7-square-mile unincorporated area, and a slice of the Village of Mamaroneck on the far side of the Mamaroneck River. All three share a Town government for some functions and run their own show for others.
The result, more than a century later, is a mailing address that outlived the municipal map it was drawn on. The Larchmont post office still serves a wide area, and a large share of the addresses it covers sit outside the incorporated village entirely.
The bill that only one side gets
Every property owner in the Town of Mamaroneck receives a combined Town and County tax bill each April, and a school tax bill from the Mamaroneck Union Free School District split into two halves, one published September 1 and due September 30, the other published January 1 and due January 31. If your specific parcel falls inside the Village of Larchmont, you get a third bill on top of those two: a stand-alone Village property tax, published June 1 and due June 30. That bill funds the Village of Larchmont Police Department, the Village's own Department of Public Works, and the nine parks the Village maintains.
If your parcel sits in the unincorporated area, you don't get that third bill. But you're not getting a discount, you're getting a different arrangement. Your April Town payment funds police, fire, and sanitation delivered directly by the Town of Mamaroneck, the same categories of service the Village bill funds through its own department instead. Even trash pickup splits along this line: Village residents are served by the joint Larchmont-Mamaroneck Sanitation Commission, while unincorporated residents get sanitation straight from the Town, which is exactly the kind of detail a buyer only learns by asking rather than by reading a listing sheet.
Same zip code, opposite direction this year
Here's where the line stops being administrative trivia and starts affecting what a house actually costs to keep. The Town of Mamaroneck releases a tentative assessment roll every summer, and this year's roll, which becomes final this September, shows the Village and the unincorporated area moving in opposite directions from where they were twelve months ago.
Between 2024 and 2025, average assessments in the Village of Larchmont rose 11.27% across all property classes and 13.14% for single-family homes specifically, the steepest increase of any area in the Town that year. The 2026 tentative roll flips that: Village assessments are projected to rise just 4.60% overall and 5.46% for single-family homes, the smallest increase in the Town this cycle. The unincorporated area ran the opposite pattern. It saw a comparatively modest 9.77% increase in 2025, and this year it's projected for the largest jump in the Town at 7.35% overall and 9.05% for single-family homes.
| Village of Larchmont | Unincorporated Town of Mamaroneck | |
|---|---|---|
| Police department | Village of Larchmont Police Dept. | Town of Mamaroneck Police Dept. |
| Extra property tax bill | Yes, published June 1, due June 30 | No |
| Total annual tax bills | Three (Town/County, Village, School) | Two (Town/County, School) |
| 2025 assessment change, all property | +11.27% | +9.77% |
| 2026 tentative assessment change, all property | +4.60% | +7.35% |
| 2025 assessment change, single-family | +13.14% | +11.27% |
| 2026 tentative assessment change, single-family | +5.46% | +9.05% |
A buyer who assumed a Village address meant the hottest assessment growth in town, because that's what happened in 2025, would be working off last year's story. The unincorporated side is now the one carrying the steeper trajectory, and since assessed value flows directly into the tax bill, a homeowner on that side watching their bill climb faster than the price they paid isn't imagining it.
This also changes who has the most at stake in a grievance. The Town's deadline to challenge an assessment, the third Tuesday in June, already passed for this cycle, but it returns every year on the same schedule. In a year like this one, where the unincorporated area is absorbing the larger jump, that's the group with more reason to file when the window reopens next June.
What else changes at the same invisible line
The school district boundary tracks the same split. Chatsworth Avenue School sits inside the Village, while Central School draws from unincorporated Town streets that carry the identical Larchmont mailing address. Both feed into Hommocks Middle School and Mamaroneck High School further down the line, so the split shows up early in a child's schooling rather than at the district level. The Mamaroneck Union Free School District's 2026-27 budget, which carried a proposed 3.07% tax levy increase, went before district voters on May 19, and whatever the outcome, that school tax rate applies across the whole district regardless of which side of the police and sanitation line a family lives on. That's the one bill everyone shares equally.
How to find out before you write an offer
None of this shows up on a listing sheet, and most portal comparables blend both jurisdictions into a single "Larchmont" median, which is part of why that number can be misleading on its own. The most reliable way to check is directly through the Town of Mamaroneck's property tax information and its FAQ on municipal boundaries, which lays out exactly which streets fall inside each jurisdiction. A buyer's attorney will eventually surface this at contract, but by then most people have already anchored to a price based on comparable sales that never distinguished between the two sides. Asking the question before you write an offer, not after you're under contract, is the difference between budgeting for the actual tax stack and being surprised by a June bill you didn't know was coming.
FAQ
Does a Larchmont mailing address mean I'm in the incorporated Village? Not necessarily. The zip code and post office name reflect the historical resort community that predates the 1891 incorporation, not the current municipal line. A meaningful share of addresses under the Larchmont zip sit in the Town of Mamaroneck's unincorporated area instead.
If I buy in the unincorporated area, is my total tax bill lower since I skip the Village tax? Not automatically. You're paying for a comparable set of services, police, fire, and sanitation, through the Town-collected tax instead of a separate Village bill. The two sides' rates and assessment growth move independently from year to year, as this year's numbers show.
When does the 2026 assessment roll become official? The Town finalizes the tentative roll in September. After that, the grievance window is closed until it reopens next June.
Knowing which line a specific block sits on is the kind of detail that only comes from working this market street by street. If you're comparing a Larchmont address to another Westchester village, or you want a clear read on what a specific parcel's tax picture actually looks like before you list or make an offer, Andrew Rogovic can walk you through it. Request a free home valuation and get the full picture, not just the zip code.
