A buyer pulls up two listings on a Saturday morning. Both addresses end in Mamaroneck, NY 10543. Both are roughly the same square footage, on roughly the same size lot, asking within 3% of each other. The buyer assumes they are choosing between two comparable houses.
They are not. They are choosing between two different bundles of taxing authorities, two possible school districts, two different bond ratings on their municipal debt, and two completely different tax-bill calendars. The price on the listing portal reflects almost none of that. In summer 2026, this is the single most important thing a relocating buyer needs to understand before writing an offer inside the 10543 ZIP code.
The bill that arrived in April, and the one arriving in June
The clearest way to feel the jurisdictional split is to look at when tax bills actually land. Town of Mamaroneck Town and County tax payments had to carry a legible United States postmark no later than April 30, 2026 to be considered timely, and the Town specifically warned that personal online banking batches often miss that postmark. Two months later, the Village of Mamaroneck told residents that Village tax bills would be mailed on or before June 5, 2026, with the 2026 and 2027 Village taxes payable after June 1.
That is one home, two separate bills, two separate offices, two separate calendars. A buyer closing in May who has only budgeted for the April Town bill is about to discover the June Village bill at the worst possible moment.
The buyer next door, in the unincorporated portion of the Town, will never see a Village bill at all. Same ZIP code. Different cash-flow profile.
Three jurisdictions, one mailing label
The 10543 ZIP code covers three distinct municipal setups. The Village of Mamaroneck and the Village of Larchmont each layer their own government on top of the Town, while a third group of homes sits in what locals call the "unincorporated area," meaning the Town with no village layered over it.
The 2026 budget cycle put real numbers on the difference. The Town's preliminary 2026 budget came in tax-cap-compliant for the first time in a while, squeaking under the 2.83% average increase automatically permitted by New York State, with the tax levy for homes in the unincorporated area rising 2.96% after an 8.81% jump the prior year, and the Town tax levies for both Villages rising 2.36% before the Villages add their own taxes. The Village of Mamaroneck then layered its own bill on top: the Fiscal Year 2026-2027 budget totals $50,328,000 while remaining under the New York State tax cap, with an adopted tax levy increase of 2.79%, approximately $911 below the allowable tax cap limit.
Three different rates, three different governments, one mailing address. And the credit profile underneath those budgets is not uniform either. Both the Town and the Village of Larchmont enjoy a AAA bond rating, while the Village of Mamaroneck rating is AA+, and Larchmont maintains a 25 to 28% fund balance ratio. For a buyer planning to hold for 10 to 20 years, those ratings hint at the cost trajectory of future infrastructure borrowing, which eventually shows up in the levy.
The river that changes your school district
The single sharpest line on the 10543 map is the Mamaroneck River.
The Mamaroneck Union Free School District serves the Town of Mamaroneck, the Village of Larchmont and the part of the Village of Mamaroneck that is within the Town of Mamaroneck, while the part of the Village of Mamaroneck within the Town of Rye is served by the Rye Neck Union Free School District. In practical terms, two houses on the same Village street can sit in two different school districts depending on which side of the river they fall on.
The municipal map underneath that boundary is just as tangled. As the Larchmont Loop laid out in its primer on the area, driving north on Boston Post Road at the New Rochelle city limit, you can never quite be sure where you are, and the roughly five-mile stretch to the City of Rye crosses a maze of jurisdictions and taxing authorities that overlap and duplicate each other. The piece counted three police departments, three court systems, three fire departments, two library districts, and two trash collection systems across that stretch.
For the buyer, this means a 10543 listing is not a single product. It is one of at least six combinations of village-or-not, school district, and library district, each with its own cost stack.
What this does to the comp set
The portal-level "Mamaroneck median" mixes all of those products together, which is why the headline number behaves erratically. Redfin's running figure for Mamaroneck home prices, as of the most recent month available, sat at roughly $1.1M with about 21 days on market and 21 sales recorded that month. A separate listings-side cut for June 2026 put the median list price closer to $848,000 at about $476 per square foot with 24 days on market. PropertyShark's Q1 2026 read came in at $1.8M on only 20 closings, a 35.5% drop in deal count year over year.
Those are not contradictory data sets. They are the same market, sliced three different ways, and the spread between them is the story. When fewer than two dozen homes close in a quarter, a handful of waterfront sales in the Orienta or Shore Acres ends of the Village can pull the median into seven figures, while a cluster of Heathcote Hill condos or Washingtonville cottages can pull it back down. The "median" is reporting which sub-market closed last, not what comparable houses cost.
Here is what the same nominal asking price actually buys across the 10543 universe:
| Same list price, different bundle | Likely village layer | School district | Town/County bill | Second bill |
|---|---|---|---|---|
| House in unincorporated Town | None | Mamaroneck UFSD | Due late April | None |
| House in Village of Larchmont | Larchmont | Mamaroneck UFSD | Due late April | Larchmont Village bill |
| House in Village of Mamaroneck, west of the river | Mamaroneck | Mamaroneck UFSD | Due late April | Village of Mamaroneck bill, mailed early June |
| House in Village of Mamaroneck, east of the river | Mamaroneck | Rye Neck UFSD | Town of Rye assessment | Village of Mamaroneck bill, mailed early June |
Two listings at $1.35M, both with 10543 mailing addresses, can carry meaningfully different effective property tax bills and meaningfully different total municipal service costs once library, sanitation, and village services are layered in. The list price is the same. The thing being sold is not.
The other quiet fact in that table: the Village of Mamaroneck stopped doing its own assessing more than a decade ago. As of October 8, 2014, the Village adopted a local law to terminate its assessing function, transferring it to the Towns of Rye and Mamaroneck, saving the Village over $100,000 per year, while continuing to send out tax bills and collect taxes for Village property taxes, with both Towns maintaining their real property rolls at full value. So a Village of Mamaroneck homeowner east of the river is assessed by the Town of Rye, billed by the Village of Mamaroneck, and educates their children through Rye Neck. Three different governments, one driveway.
Reading a 10543 listing in summer 2026
Before writing an offer, a buyer in this ZIP code should resolve four questions in this order:
- Which village layer, if any, applies. The Village of Mamaroneck has its own tax bill mailed in June; the Village of Larchmont layers its own bill; the unincorporated Town has none.
- Which school district the parcel falls into. The Mamaroneck River, near Harbor Island Park, is the dividing line between Mamaroneck UFSD and Rye Neck UFSD inside the Village.
- Which Town assesses the parcel. East of the river inside the Village of Mamaroneck, that is the Town of Rye, not the Town of Mamaroneck.
- Whether the seller's posted taxes reflect the most recent levy. In the Town of Mamaroneck, the Valuation Date is July 1st of the prior year, so assessments on the 2026 assessment roll are based on the value of the property as of July 1, 2025, and the most recent levy increases for the Town and Village did not appear on portal-cached tax figures until well after the 2026 budgets were adopted.
That fourth question matters because grievance windows are narrow. The Board of Assessment Review convenes on the third Tuesday in June, which is Grievance Day, and a buyer closing after that date carries the assessment forward until the following year.
A short FAQ
If the address says Mamaroneck, am I in the Village of Mamaroneck? Not necessarily. The 10543 ZIP covers parts of the Village of Mamaroneck, the Village of Larchmont, the unincorporated Town of Mamaroneck, and a sliver of the City of Rye. The mailing label is a Postal Service convenience, not a municipal boundary.
Why do I see two very different median price numbers for "Mamaroneck" on different sites? Because the closings are thin and the mix swings hard. Q1 2026 closed only about 20 single-family deals, so a few high-end Orienta sales versus a few entry-level Washingtonville sales can move the median by hundreds of thousands of dollars without any underlying change in value. The number to ask for is the sale-to-list ratio and days on market for the specific sub-market your target house sits in.
Does the school district line really run down the Mamaroneck River? Yes, at the Village level. East of the river inside the Village of Mamaroneck is Rye Neck UFSD, whose middle and high schools sit on a shared campus on Hornidge Road. West of the river is Mamaroneck UFSD. Two Village neighbors can be in two different districts.
When is the worst time of year to close, cash-flow wise? Late May through early June. A buyer who closed in late April just inherited a fresh Town and County bill, and is days away from a Village bill arriving in the mailbox. Plan the prorations and the closing escrow accordingly.
The 10543 ZIP code rewards buyers who treat the mailing label as the start of due diligence, not the end of it. If you're weighing two homes in Mamaroneck and want a straight read on what each one will actually cost to own, how the school district line affects resale, and where the offer math really lives, Roseanna Tedone would be glad to walk through the specifics with you. Let's Connect.
