Even a small ownership stake in Salesforce Tower, San Francisco’s tallest building, is worth nine figures.

Owner Boston Properties said in a recent corporate filing that it paid $187 million last year to buy out minority partner Hines, which owned 5 percent of the building.

A $187 million payment for a 5 percent ownership stake suggests Salesforce Tower is now worth more than $3 billion. But there are a few details to consider.

The deal included Hines’ 5 percent stake in the building as well as an “additional promoted payment based on the success of the property,” according to a Securities and Exchange Commission filing. Hines won the competition to build the project, then known as the Transbay Tower, in 2007. It later brought in Boston Properties, one of the country’s biggest office owners, as an equity partner.

The additional payment amount wasn’t specified, so the tower’s total valuation is unclear.

Older San Francisco office buildings have sold for upward of $1,300 per square foot in the past year. A 49 percent ownership stake in Park Tower, a new building near Salesforce Tower, is expected to trade for more than $1,500 per square foot, The Chronicle previously reported. Based on those price ranges, Salesforce Tower could be worth more than $2.1 billion, but the building isn’t for sale.

The Boston Properties and Hines transaction is one of the Bay Area’s largest real estate deals in the past year, but it’s unclear whether San Francisco will see any boost in tax revenue from it.

Salesforce Tower’s 5 percent ownership change is far below the threshold — a more than 50 percent ownership change — that triggers a one-time transfer tax, said Jeffry Bernstein, a partner at law firm Coblentz Patch Duffy & Bass who specializes in tax law.

It’s unclear whether the deal will affect Salesforce Tower’s assessed property value, which was $1.33 billion for the 2017-18 fiscal year, making it the most valuable building in the city. The city will release new property assessments in July.

Boston Properties didn’t provide details on how Salesforce Tower was valued in its transaction with Hines.

“We’re in discussions with the city assessor right now, and it’s just not appropriate to discuss how the valuation was done and what it was,” Mike Labelle, Boston Properties chief financial officer, said in a Wednesday earnings call. Boston Properties and Hines declined to comment.

Under California’s landmark 1978 property tax law Proposition 13, building values can rise no more than 2 percent a year, which shields both corporate owners and individual homeowners from spikes in taxes. Two exceptions are when more than 50 percent ownership in a building is sold or when a new building is completed.

Most valuable San Francisco buildings 1. Salesforce Tower, 415 Mission St., $1.33 billion, 1.4 million square feet 2. 555 California St., $1.01 billion, 1.8 million square feet 3. 101 California St., $984 million, 1.2 million square feet 4. One Market Plaza, $834 million, 1.6 million square feet 5. Westin St. Francis, 345 Powell St., $718.5 million, 500,000 square feet 6. 50 Fremont St., $689.3 million, 817,000 square feet 7. Chase Center, 300 16th St., $659 million, 680,000 square feet 8. The Exchange, 1800 Owens St., $558.1 million, 750,000 square feet 9. Parc 55, 55 Cyril Magnin St., $512.2 million, 696,431 square feet 10. One Front St., $510 million, 638,000 square feet Based on city property assessment, fiscal year 2017-18 Source: San Francisco Assessor-Recorder Salesforce Tower by the numbers Assessed value: $1.33 billion (2017-18 fiscal year) Estimated value: $2.1 billion Height:1,070 feet Size: 1.4 million square feet Rent paid by Salesforce: $50 million a year Source: Chronicle research

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Salesforce Tower falls into the new building category in the current 2018-19 fiscal year, said Douglas Legg, deputy director of operations at the city’s Office of the Assessor-Recorder, which oversees property taxes.

Last year’s $1.33 billion calculation was based on the tower’s construction costs and came shortly before the building opened, Legg said. He expects that number to go up this year but doesn’t know by how much because the city hasn’t done an appraisal. Office buildings are typically valued based on their rental income, he said.

Legg said he isn’t aware of any discussions between the Assessor-Recorder’s Office and Boston Properties related to the recent deal with Hines.

Boston Properties said in SEC filings that Salesforce Tower is fully leased, and that it generated net operating income of $11.3 million in the last three months of 2018.

Salesforce leases 882,000 square feet, or nearly two-thirds of the 1.4 million-square-foot tower. Salesforce said in SEC filings that it’s paying nearly $50 million a year in rent.

Other tenants include co-working firm WeWork, consulting giants Accenture and Bain & Co., law firm Covington & Burling, private equity company Hellman & Friedman and real estate brokerage CBRE.

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf