A developer named Ramtin Ray Nosrati just put a five-bedroom spec mansion on the market for $35 million. The house sits at the end of a cul-de-sac on Donhill Drive, runs about 15,000 square feet, and comes with roughly $2 million in custom furniture already inside. The mailing address says Beverly Hills, 90210.
Hoodline reports that, if it sells at that number, the seller owes the City of Los Angeles close to $1.9 million at closing. Not because of the price tag alone, but because Donhill Drive sits inside the municipal boundaries of the City of Los Angeles, not the incorporated City of Beverly Hills. A house two streets over, technically inside the actual city limits, sits across that boundary.
Same zip code. Same general hillside. Different tax treatment.
Why the Zip Code Doesn't Tell You What You Think It Does
The 90210 zip code was drawn by the postal service in 1963, and it never mapped cleanly onto the city's actual borders. When Beverly Hills incorporated in 1914, its northern edge stopped roughly a mile short of Mulholland Drive. Everything above that line, stretching up through the canyons, stayed part of unincorporated Los Angeles even though the Beverly Hills post office picked up the mail. Locals started calling it Beverly Hills Post Office, or BHPO, and the name stuck because it was useful. It described a real distinction that the zip code papers over.
That distinction used to be about services. BHPO residents get LAPD and LAFD, not the Beverly Hills Police and Fire Departments. Their kids are zoned to Los Angeles Unified schools, not Beverly Hills Unified.
In 2026, the distinction is about money, and the stakes are far higher.
What the Line Actually Costs
Los Angeles voters approved Measure ULA in November 2022, a transfer tax on real estate sales inside the City of Los Angeles. As of July 1, 2026, the thresholds sit at $5.4 million and $10.9 million, with a 4 percent tax between those figures and 5.5 percent above the top line. Beverly Hills, because it governs itself as an independent city, is not inside Los Angeles and pays none of it. BHPO, because it is unincorporated Los Angeles wearing a Beverly Hills mailing address, pays every bit of it.
A few real transactions from this year show what that means in dollars, not theory.
| Property | Jurisdiction | 2026 status | Price | Tax at closing |
|---|---|---|---|---|
| Donhill Drive spec mansion, listed September 2026 | City of Los Angeles (BHPO) | Subject to Measure ULA | Asking $35M | Roughly $1.9M if sold at ask |
| Hidden Valley Estates home, sold March 2026 | City of Los Angeles (BHPO) | Subject to Measure ULA | $17.1M | Triggers the 5.5% tier |
| Hillcrest Road estate, Trousdale Estates | City of Beverly Hills | Fully exempt | $20M | $0 ULA |
The Hidden Valley sale belonged to television writer Kevin Williamson, the creator behind Scream and Dawson's Creek, who bought the home in 2020 for $17 million and sold it this March for $17.1 million. Because Hidden Valley Estates sits inside BHPO, that sale crossed into the tax's top bracket even though the house barely appreciated in six years. A comparable estate on Hillcrest Road in Trousdale Estates, fully inside Beverly Hills city limits, closed around $20 million with no transfer tax obligation attached at all.
That gap does not shrink as prices go up. It grows. The exemption itself is not new: Beverly Hills homes were outside ULA from the start, including the home actors Joe Manganiello and Sofia Vergara listed for around $18 million in 2023. What has changed since is the size of the bill on the other side of the line, now that the top bracket starts at $10.9 million.
The 1954 Decision That's Still Paying Off
There is a neighborhood that solved this problem seven decades before Measure ULA existed, and the way it did so is the clearest illustration of why the boundary matters more than the brand name.
In 1954, developer Paul Trousdale bought a stretch of the old Doheny Ranch above Sunset Boulevard and asked the Beverly Hills City Council to annex it into the city rather than leave it in the surrounding Los Angeles hills. The council agreed, Trousdale subdivided the land into 532 lots, and Trousdale Estates became part of Beverly Hills proper rather than another BHPO enclave. At the time, the appeal was city services and a Beverly Hills mailing credential that meant something to buyers.
Nobody in 1954 was annexing land to dodge a transfer tax that wouldn't exist for another 68 years. But that is exactly the advantage Trousdale Estates carries into 2026. A house on Loma Vista Drive sits inside the same municipal boundary that exempts the rest of Beverly Hills, while a house a few canyons over in Beverly Crest or Benedict Canyon, both part of BHPO, does not. The zoning decision that mattered for prestige in 1954 is the decision that determines a seven-figure tax bill today.
The Clock Nobody Selling Right Now Can Ignore
The math above assumes the current version of Measure ULA holds through the fall, and that assumption is shakier than it looks from where we sit in September.
Reed Corp reports that the Howard Jarvis Taxpayers Association has spent much of 2026 pushing a statewide ballot initiative aimed at the November election that would cap local transfer taxes like ULA. The Los Angeles City Council took its own swing at the measure in January, considering a rewrite that would have added a 15-year exemption for new construction and hardship relief for owners affected by the 2025 Palisades fire, then declined to send that reform to voters. In June, the council reversed course and voted 9 to 5 to draft a narrower ballot measure of its own, one that would carve out new multifamily construction and Palisades fire sales from the tax.
None of that has resolved as of this writing. A seller listing a BHPO property this fall is pricing a deal against a tax regime that could look different by December, and a buyer negotiating a BHPO purchase right now is negotiating against the same uncertainty. That is not a reason to freeze. It is a reason to build flexibility into how a deal is structured, particularly around timing, rather than assuming today's bracket is the only bracket that will ever apply.
What This Actually Means If You're Comparing Addresses
The practical habit worth building is simple: stop reading the zip code as a jurisdiction and start confirming the actual city line before you model net proceeds on anything priced above $5 million on the Westside. A title company or escrow officer can confirm municipal jurisdiction in minutes, and the difference it reveals is not cosmetic. It is the difference between a seller keeping an extra $1.9 million or writing that check to the city.
This is not unique to Beverly Hills and BHPO. The same line runs through Bel Air, Brentwood, and Pacific Palisades, all technically inside the City of Los Angeles and therefore inside ULA's reach, while Santa Monica and Culver City are separate cities. Anyone comparing a Westside estate to a Beverly Hills flats property is not just comparing square footage and finishes. They are comparing tax exposure before either side signs anything.
Does Bel Air pay the mansion tax?
Yes. Bel Air sits inside the City of Los Angeles, so sales above the current thresholds are subject to Measure ULA the same way BHPO sales are.
How do I find out if a 90210 address is actually inside Beverly Hills?
The zip code alone will not tell you. A title company, escrow officer, or the city's own boundary records can confirm whether a specific address sits inside Beverly Hills city limits or in the surrounding Los Angeles jurisdiction.
If the November ballot measure passes, does it apply to deals that already closed?
That has not been settled publicly as of this writing, and it is one more reason to talk through timing with your advisor before locking in a closing date this fall.
Whether you're comparing a hillside listing in Beverly Crest to one in Trousdale, or trying to understand what a Bel Air address actually costs you at closing compared to a Beverly Hills one, the boundary line matters more than the brand name on the mailbox. Simon Mashian works these distinctions daily across Beverly Hills and the Westside, and can walk you through what a specific address actually owes before you write an offer or set a list price. Let's Connect.
This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.
