LA’s “mansion tax,” sold to Angelenos as a way to tax the rich and boost housing, has instead blocked the building of 9,100 homes, wiped out 16,650 full-time construction jobs and cost $452 million in revenue.

A damning new report says the tax, officially known as United to House LA, or ULA — has had a negative impact on the city’s high-end and multi-family real estate markets and collected less than half what it was expected to generate to tackle the city’s housing crisis.

The ULA was expected to raise about $900 million a year, or $2.7 billion over its first three years. Instead, it brought in about $1.2 billion.

The tax — which went into effect in April 2023 and was championed by socialist mayoral hopeful Councilwoman Nithya Raman — means if a property in LA sells for more than $5.4 million, the seller is taxed 4% of the price at closing. If it sells for more than $10.9 million, it increases to 5.5%.

Despite its nickname, LA’s “mansion tax” applies far beyond luxury homes. Apartment buildings, offices, warehouses and vacant land can all trigger the tax if they sell above the thresholds.

About 1,000 of the 9,100-plus new homes lost would have been affordable units — the very thing the tax was supposed to create — according to RAND corporation, a non-partisan, nonprofit research group.

Westside real estate broker Danny Brown told The California Post the tax was ”another disaster initiated by the incompetent socialists who run our city.”

“ULA has chopped the legs from under the residential and commercial real estate industry, which is one of the largest parts of our city’s economic engine,” Brown said.

Mayor Karen Bass did not take a position on the mansion tax, but Raman has since said she was in favor of reforming the tax.

RAND found the ULA slashed high-value property sales by an estimated 31% through early 2026, with apartment and commercial sales falling by more than 46%.

Simply put, the tax has discouraged some owners from selling and developers from pursuing projects that, because of the tax, no longer make financial sense.

“Measure ULA has the noble aspiration of delivering more affordable housing inventory to Los Angeles, but its negative repercussions may outweigh its benefits. A transfer tax of this type adds friction to the housing market and slows the number of home transactions,” Joel Berner, a senior economist at Realtor.com, told The Post.

Realtor.com is owned by News Corp, the same parent company that owns The Post.

“Builders are already dealing with high costs of labor and materials, so this added expense when they go to sell a completed or revitalized project squeezes their margins even further,” Berner added. “This will lead some to decide that the deals simply are not worthwhile.”

New research has documented a significant hit to high-value property sales and housing development since ULA took effect in 2023.

The tax also wiped out the equivalent of 16,650 full-time construction jobs and cost government agencies $452 million in lost revenue, according to RAND.

And the City has barely touched the cash, spending just $114 million as of May — less than 10% of the money raised. The City Council voted 13-0 last Tuesday, Raman included, to put a record $466.6 million toward affordable housing, with $324 million of that — nearly 70% — coming from ULA.

But when the tax passed, Raman couldn’t stop bragging.

“This is truly the first housing initiative of its kind anywhere in the United States that will have such a widespread, immediate, and long-term impact on the housing and homelessness crisis,” she said.

One property in Brentwood, the Westside enclave long favored by Hollywood stars and pro athletes, shows how the tax can play out in the real world.

The property sold for about $5.3 million in February 2023, weeks before ULA took effect.

The original house was torn down and replaced with a new 8,990-square-foot, seven-bedroom home with a pool, screening room and guest house. It hit the market last December at $19.995 million. After three price cuts, it’s now listed at $15.995 million.

If it sells at that price, the ULA bill would be about $880,000.

Brown showed The Post around the block and said even the modest older houses next door could get hit because the land beneath them alone is worth more than $5 million.

“It’s 2,000 feet. Not a mansion, even though it’s $5.5 million, because of the land it’s sitting on,” Brown said. “Sounds good to tax the millionaires and billionaires. Everyone says, ”great,” but it’s so far from reality of what happens.”

For builders, that additional cost reality hits even harder.

Developer Barry Cassily said developers already operate on threadbare profit margins, and now have to factor in an additional 4 to 5.5% bite out of qualifying sales, potentially making some projects financially unworkable.

“You are taxing housing to pay for housing,” he said.

Critics say the result is builders have stopped building and owners stop selling.

Fewer sales also means less property tax revenue, because in California, a property is reassessed to its current market value when it changes ownership.

A study by UCLA’s Michael Manville and USC’s Mott Smith, covering about 338,000 LA County property sales, has found a sharp decline in transactions above ULA’s threshold.

“If in the meantime, you’ve deterred hundreds or thousands of market-rate units, you have not helped affordability,” Manville, who chairs UCLA’s urban planning department, told The Post.

He called it “robbing Peter to pay Paul.”

Manville says the report takes into account other economic factors such as high interest rates. Researchers at Occidental College, meanwhile, argue broader economic conditions better explain the decline in multifamily development.

Their analysis suggests that the slowdown in apartment construction was part of a wider trend affecting development, making it difficult to isolate the tax’s impact from other economic pressures.

Jason Oppenheim, the luxury broker who stars on Netflix’s “Selling Sunset,” claims RAND’s numbers through September show as many as 10,600 apartments were deterred, against roughly 1,900 new units ULA has helped fund.

“City Hall is celebrating the housing it funds from Measure ULA while ignoring the far greater number of apartments its tax is preventing,” Oppenheim told The Post.

Even those 1,900 units come with an asterisk, with the ULA only typically funding one part of affordable housing projects.

Manville compared the city’s claim to old TV ads calling Froot Loops “part of this nutritious breakfast.”

“It is a part of that breakfast,” he said. “But, like, how big of a part really?”

Raman has since tried to change the tax, proposing earlier this year to exempt newly built apartment, commercial and mixed-use projects from ULA for 15 years.

“A policy that unintentionally stalls housing production ultimately undermines the very goals voters asked us to achieve,” Raman said.

However, her proposal failed to make the June ballot amid fierce opposition from labor and pro-ULA groups.

Bass hasn’t been a ULA purist either.

Last year, the mayor tried to rewrite the tax in Sacramento, then pulled the bill at the last minute after ULA backers revolted.

Weeks later, after meeting with billionaire developer Rick Caruso, she asked the council to give Palisades fire victims a three-year break from the tax.

And some of the money isn’t building anything new.

In April, the city steered $55.5 million toward preserving 3,713 existing affordable units. About $2 million went to 11 buildings run by SRO Housing Corp.

One of them, the 96-unit Renato Apartments, got $100,000. In a 2024 lawsuit, tenants alleged they lived with bedbugs, cockroaches, rats, sewage leaks and human waste, court papers show.

SRO Housing has lost $27.8 million since 2022 and has warned the city it will collapse without more public money, Politico reported this month.

Manville said keeping existing units livable isn’t automatically a bad use of the money.

“If for a small amount of money we can take some units that are at risk of being declared uninhabitable and keep them on the market, that could very well be a policy win,” he said.

Councilwoman Imelda Padilla, who took over the council’s new Housing Committee in August after the committee Raman chaired was broken up, has pushed for quarterly reports on where the money goes.

“We must follow these dollars and ensure they are producing the affordable housing Angelenos deserve,” Padilla told The Post.

ULA’s citizen oversight committee did not respond to The Post’s request for comment.

Applications for the $466.6 million funding round open Oct. 13 — three weeks before voters decide whether Raman gets the keys to City Hall.