A buyer under contract in Riverside this spring is inheriting a tax bill their comps cannot see. Sellers' most recent bills reflect the 2021 Grand List. The October 1, 2025 revaluation, mailed as preliminary notices on November 10, 2025 by J.F. Ryan & Associates on behalf of the Town, does not hit paper until the July 1, 2026 bill. The mill rate the Board of Estimate and Taxation will set in May 2026 will apply to an assessed value most buyers have never seen and most sellers had until February 20, 2026 to appeal.
That is the transaction friction. The market story underneath it is bigger, and it starts with the number every portal shows first.
One median, five products
In November 2025, Riverside home prices were up 10.4% compared to last year, selling for a median price of $4.7M. On average, homes in Riverside sell after 29 days on the market compared to 33 days last year. There were 9 homes sold in November this year, up from 5 last year. Price per square foot ran near $1,060, a figure that on its face implies broad appreciation.
It does not. Riverside is a compact neighborhood bordered by the Mianus River to the west, Long Island Sound to the south, and Palmer Hill Road to the north, and inside that footprint the Town's Building Zone Regulations sit five different residential zones on top of each other. That is why a 10-fold difference in sales prices [exists]. In 2021 we had 157 sales in Riverside and the prices varied from our lowest Riverside sales price of $705,000 in the R-7 to a $7,800,000 sale in the RA-1 zone.
The FAR envelope, more than the lot, controls what a buyer can actually build:
| Zone | Min lot | FAR | Approx. allowed above-grade | Where it sits |
|---|---|---|---|---|
| RA-1 | 1 acre | 0.135 | ~5,881 sf | Between I-95 and the Sound; includes gated private associations |
| R-12 | 12,000 sf | 0.315 | ~3,780 sf | Northern Riverside and inside the Riverside Ave loop |
| R-7 | 7,500 sf | 0.35 | ~2,625 sf | North side of the Post Road |
| R-6 | 7,500 sf | — | Two-family permitted | Two parcels only |
| Overlays | — | — | — | Historic and conservation |
This FAR limitation doesn't apply to the basement, if it isn't a walkout basement, nor to the attic, so you could have over 6,000 s.f. for new construction on four levels in an R-12, which is why teardown pricing on quarter-acre lots does not track linearly with the lot itself. The FAR envelope is the product. The land is a container for it.
What I-95 actually divides
The highway is not a neighborhood line. It is a product line. South of I-95 the RA-1 zone reaches to the water and folds in private associations that locals sometimes label Little Belle Haven, several of them gated. The Riverside Yacht Club, founded in 1888 and the second-oldest club of its type in Connecticut, anchors the shore. Waterfront listings with private beach access have historically crossed $10 million.
North of I-95 the stock shifts to R-12 and R-7 cottages and colonials of an earlier building era, oriented around the Riverside Ave commercial spine, Riverside Commons, and the Old Greenwich-Riverside Community Center. It is the same zip code, the same schools, the same 06878, and a different asset entirely.
A buyer who reads a 52% year-over-year jump in price per square foot as evidence of broad appreciation is misreading a mix shift. The RA-1 tier transacted more heavily against a thin comp set. The R-12 buyer north of the highway is not shopping in a plus-52% market. She is shopping in a market where supply is extremely tight at 1.6 months, the lowest in the market. The $2M–$3M bracket is the hottest segment: 19 days on market with a sale-to-list price of 102.9% across Greenwich as a whole, and where Riverside's own north-of-95 inventory is being reached by buyers priced out of RA-1 stock.
The revaluation is the friction most spring buyers will miss
Connecticut requires each municipality to revalue every five years. The Town's 2025 Revaluation page confirms the timeline: Preliminary assessment notices were mailed out to all property owners on November 10, 2025. This new assessment reflects 70% of the fair market value of your property as of October 1, 2025. This assessment will be effective on the July 1, 2026 tax bill. The Board of Estimate and Taxation shall set the new mill rate in May 2026, which shall be reflected in the July 2026 tax bill.
The dates that matter to a Riverside transaction closing between now and midsummer:
- November 10, 2025: Preliminary assessments mailed. Sellers had them in hand before most spring listings hit.
- Mid-November 2025 to mid-January 2026: Informal hearings with J.F. Ryan & Associates. Closed.
- February 1 to February 20, 2026: Formal appeals to the Board of Assessment Appeals. Closed.
- March 2026: BAA hearings.
- May 2026: BET sets the new mill rate against the reset Grand List.
- July 1, 2026: New assessment hits the tax bill, due August 1, 2026.
- October 1, 2030: Next revaluation.
The Chair of the BET has publicly explained the mechanic that catches people: The Mill Rate calculated by dividing the Town Budget by the Grand List. When the Grand List increases significantly due to a revaluation, all else equal, the Mill Rate automatically adjusts downward. That sounds neutral. It is not evenly distributed.
Walkable, high-demand pockets absorbed most of the appreciation between the 2021 and 2025 Grand Lists. Riverside sits inside that group. A rate that drifts downward against a larger town-wide base can still land as a materially higher bill on a Riverside parcel whose assessed value moved faster than the town-wide average.
The FY25-26 headline rate of 12.041 mills, applied to 70% of fair market value, produced roughly $16,857 in annual property tax on a $2M home and roughly $25,286 on a $3M home. Both numbers reset in July. Sewer district parcels also carry a 0.278 maintenance mill and a 0.040 improvement mill, which do not appear on the headline figure.
How to price a Riverside comp in the transition year
- Do not lift the median. Verify the zone on the parcel before you use a sold comp. An RA-1 sale in Harbor Point does not price an R-12 on Bonan Drive.
- Read PPSF against FAR headroom. A cottage on an under-built R-12 lot has renovation optionality that a fully built RA-1 does not. The comp that matches the buildable envelope matters more than the comp that matches the address.
- Ask for the November 2025 assessment notice, not the last tax bill. The bill in the seller's disclosure packet reflects the 2021 Grand List. The notice reflects the number that will drive the July 2026 bill.
- Model both mill rate scenarios. The BET has not set the FY26-27 rate yet. Run the assessed value at the current 12.041 and at a plausible downward-adjusted rate. The delta is the negotiating room.
- Check for sewer district and any coastal overlay charges on the specific parcel before treating the mill rate math as complete.
- Confirm the parcel is not inside a private association with dues, road maintenance obligations, or restrictions that do not appear on the field card.
FAQ
Can a buyer inherit the seller's revaluation appeal? No. The Assessment appeals to the BAA must be in writing on the prescribed form and postmarked or hand-delivered to their meeting room in Town Hall designated for the Board of Assessment Appeals no later than Friday, February 20, 2026. That window has closed. A buyer who takes title after February 20 has no standing to file for the current cycle and waits until the next event.
When can this be revisited? Greenwich's next revaluation will be for the October 1, 2030 Grand List. In the interim, the Assessor can adjust an assessment only for narrow reasons: new construction, demolition, a change of use, a factual error, or a court order.
Does Greenwich's low mill rate offset a higher assessment? Not automatically. Greenwich's 12.041 is lower than Darien's 15.48 and New Canaan's 16.69, but the tax bill is the product of rate and assessed value. A larger reset assessment can produce a bill that exceeds a peer town's, even at a lower rate. Run the math on the specific parcel.
Work the number, not the median
The $4.7M headline is a starting question, not an answer. What that number actually buys depends on which of Riverside's five zones the parcel sits in, which side of I-95 the buyer is standing on, and what the November 10, 2025 assessment notice says the July 2026 bill will be. For a discreet read on a specific Riverside parcel, its FAR envelope, and its post-revaluation tax exposure, Konstantine G Wells is available for a private consultation or a complimentary home valuation.
