Prop 42 Passes: California Locks Its Billionaire Wealth Off-Limits

California voters approved Proposition 42 with 51.6% of the vote as of Nov. 10, with roughly 83% of ballots counted, according to Associated Press estimates published by KQED. The constitutional amendment bars new state taxes on personal property — business interests, intellectual property, financial assets — and blocks most retroactive taxes.

Its sponsor, the committee Building a Better California, drew $102 million from Google co-founder Sergey Brin. Per the California Fair Political Practices Commission, the committee spent more than $300 million across the ballot: defeating Proposition 40, the one-time billionaire tax, and passing Propositions 41 and 42. Proposition 41 failed.

The takeaway: with Prop 40 dead, Prop 42 stands alone, walling off a pool of wealth lawmakers had never taxed but were always free to reach.

What did the billionaires actually do?

Backers warned a wealth tax would drive the richest residents out. The New York Times reported venture capitalist Peter Thiel and Google co-founder Larry Page were considering leaving; Fortune reported in January that Page and Brin were cutting ties with California. Gov. Gavin Newsom echoed the exit warning.

Brin, who now lists a Nevada address, compared the billionaire tax to the Soviet-era socialism he fled as a child.

The numbers behind the fight are smaller than the rhetoric suggests. Academics who helped write Prop 40 estimated California's billionaires pay about $3 billion a year in state income tax — roughly 2.5% of income tax revenue and about 1% of total state revenue. Hoover Institution economists put it at $3.3 billion to $5.8 billion. The nonpartisan Legislative Analyst's Office estimated billionaire departures under Prop 40 would cost under $1 billion a year; the top 2% of earners pay about half of all state income taxes.

Reporting by the New York Times and CalMatters showed Props 41 and 42 were designed to nullify Prop 40 — if the billionaire tax passed, it would have been voided had either rival measure drawn more votes. Prop 40 lost statewide despite support in San Francisco and Los Angeles counties; Santa Clara County, Silicon Valley's heart, voted it down.

In plain words: the billionaires spent big on a kill switch, and it worked.

What does Prop 42 put off-limits?

Backers pitched it as protection for ordinary savers. "Proposition 42 permanently protects pensions, 401(k)s, IRAs and other personal savings from new taxes, whether proposed by the Legislature or at the ballot box," said Brian R. Marvel, president of the Peace Officers Research Association of California, which donated $150,000 to the Yes on 42 campaign.

Critics call that misleading: Prop 40 reached retirement savings only through billionaires' Roth IRAs and similar accounts worth more than $10 million. "Don't be fooled — Prop. 42 is not really about protecting your retirement savings from new taxes," Suzanne Jimenez of SEIU-United Healthcare Workers West, which sponsored Prop 40, wrote in the official voter guide. "It's a redundant, expensive trick to allow approximately 200 billionaires to keep avoiding paying their own taxes while YOU get stuck with the bill."

California already taxes few assets beyond real estate (capped by Proposition 13), boats, planes, business equipment and vehicles. Under "stepped-up basis" (heirs owe nothing on gains built up during the original owner's lifetime), untaxed appreciation flows to heirs untouched — a break the California Budget & Policy Center estimates costs the state about $5 billion a year. Prop 42 largely locks that wealth out of reach.

Could a capital-gains fight land in court?

Three law professors who helped draft Prop 40 — Brian Galle of UC Berkeley, David Gamage of the University of Missouri and Darien Shanske of UC Davis — warn Prop 42 could reach Proposition 3, which makes permanent a tax increase on the top 2% of earners, largely for education, that was set to expire in 2031. Because the measure bars taxes on "ownership or control" of personal property without defining the phrase, a court could find taxing capital gains is a tax on "financial assets."

Yes on 42 spokesperson Nathan Click called the claim "total BS" in the San Francisco Examiner: Prop 42 "was carefully crafted to only prohibit new taxes on retirements, savings and personal property, and to prohibit retroactive taxes," leaving schools, public safety and healthcare funding "untouched."

Kayla Kitson of the Budget & Policy Center said the question "could end up in courts and would depend on how broadly courts interpret the language of the measure." She declined to predict the outcome.

What does this mean for California's budget?

Prop 42 also bars retroactive taxes except in declared emergencies. Kitson pointed to the 2024-25 budget talks, when Newsom and the Legislature moved a limit on business tax credits back to the 2024 tax year, which "raised revenue more quickly to prevent deeper budget cuts." The emergency exception likely wouldn't cover such moves, she said, since it requires revenues falling "substantially" below projections.

The squeeze is real: H.R. 1, the federal "Big Beautiful Bill" passed in July 2025, is expected to cut about $30 billion a year from Medi-Cal, per the California Health Care Foundation. Medi-Cal covers more than half the state's children, 2.2 million seniors and people with disabilities, and 1 in 5 working Californians. Prop 40 was meant to fill those gaps.

Backers vow to keep pushing, and Nobel laureate economists who supported the idea predict it will spread to other states. In California, though, any new wealth tax now needs voters to undo Prop 42 first.

Brin, meanwhile, still works out of Google's Mountain View headquarters, Business Insider reported. He spent $102 million to kill a tax — and made the next one much harder to pass.