Sergey Brin is biggest donor against California wealth tax; could owe $13 billion

California Proposition 40 is a proposed one-time wealth tax. It would apply to the state's 200 billionaires if voters approve it in November. Unlike a regular yearly tax, it would target the value of their accumulated wealth at one point in time. The proposal matters because it could create a large new source of funding for public programs.

The tax rate would be 5%. The article estimates that Sergey Brin, whose net worth is nearly $260 billion, could face a bill of about $13 billion. The measure would direct 90% of its revenue to California's health care program. The remaining 10% would support education, food assistance and administration.

Supporters say Proposition 40 could generate about $100 billion over five years. Opponents, including Governor Gavin Newsom and several billionaires, argue that wealthy residents and businesses could leave. The measure will appear on the November ballot, making its effects depend on voter approval.

Sergey Brin has donated $102 million to Building a Better California, the political action committee opposing Proposition 40. That contribution makes him the single largest founder of the anti-tax effort. The campaign is also supporting pro-business, housing and infrastructure policies. Opposition groups together have raised more than $187 million, far ahead of the roughly $32 million raised by supporters.

Brin's possible exposure is much larger than his political contribution. The proposal would impose a one-time 5% tax on billionaire wealth. With a net worth of nearly $260 billion, Brin could owe about $13 billion if voters approve the measure. That estimate reflects the proposed rate applied to the wealth figure cited in the article.

Brin now lists Nevada as his residence in state records. He also reportedly bought a $51 million home near Miami Beach. Those details add to the debate over whether wealthy people might change their residences or move assets before the tax takes effect.

Proposition 40 would target California's 200 billionaires. It is not described as a tax on all residents or all businesses. The proposal would charge eligible billionaires a one-time 5% levy on their wealth if voters approve it in November. That makes the measure unusually focused: a small group of extremely wealthy people would provide the funding.

The largest share, 90% of the revenue, would go to California's health care program. The remaining 10% would be divided among education, food assistance and administration. For example, Sergey Brin's nearly $260 billion net worth could produce an estimated $13 billion bill under the proposed rate. The article does not provide separate dollar amounts for each smaller program.

Supporters estimate that the tax could generate about $100 billion over five years. Opponents argue that wealthy residents might leave, reducing other tax collections. The final outcome depends on the November vote and on how much taxable wealth remains connected to California.

If wealthy residents move their residences or assets, California could lose income-tax payments and other economic activity linked to them. Governor Gavin Newsom argues that Proposition 40 could erode the state's tax base and reduce revenue for social services. He specifically warned about possible effects on education, teachers, librarians, childcare, firefighting and police.

The mechanism is a trade-off. A wealth tax could collect a large one-time amount, but leaving billionaires might reduce future income-tax revenue. The article reports that California billionaires paid about $4.1 billion in state income taxes last year. That amount was roughly 0.2% of their combined $2 trillion net worth.

Opponents say wealthy people and businesses could leave California. However, researchers cited by Fortune argued that even if every billionaire left, lost income-tax revenue could take decades to offset the projected wealth-tax revenue. The eventual effect would depend on how many people moved and how much wealth left.

Some billionaires oppose Proposition 40 because its one-time 5% charge could produce extremely large bills. Sergey Brin could owe about $13 billion, while Eric Schmidt and Peter Thiel have also donated to opposition groups. Brin compared the proposal with the socialist society he left behind. Their broader concern is that wealth, businesses and investment could leave California.

Governor Gavin Newsom shares the opposition, though his argument focuses on public finances. He says the measure could erode California's tax base and reduce revenue for social services. He warned that investment in education, teachers, librarians, childcare, firefighting and police could suffer. This reflects a concern that losing ordinary tax revenue might outweigh the new levy.

Supporters present a different calculation. They estimate Proposition 40 could generate about $100 billion over five years, with most going to health care. The debate therefore centers on whether California gains more from collecting the wealth tax or loses more when wealthy residents and businesses move.

The article describes relocation and asset movement as possible ways wealthy people may reduce their exposure. One option is changing a legal or listed residence. Another is placing assets, family-office operations or nonprofit organizations outside California. The article does not describe a formal exemption or a guaranteed method for avoiding Proposition 40.

Sergey Brin now lists Nevada as his residence, according to state records. He reportedly bought a $51 million home near Miami Beach in March. These moves are presented alongside the wider concern that wealthy residents could leave California. They do not, by themselves, establish whether Brin has avoided the proposed tax.

Larry Page has also moved several assets out of California. His family office, Koop, was incorporated in Delaware in December 2025. Oceankind, the ocean science nonprofit founded by his wife, Lucy Southworth, was incorporated there around the same time. The article presents these developments as evidence of movement, while the tax's final impact remains uncertain.

The article focuses on a wealth tax but does not define how it differs from an income tax. In general, an income tax applies to money earned during a period, such as wages, business income or investment returns. A wealth tax applies to the value of assets a person already owns, such as shares, property or other holdings. Proposition 40 would be a one-time charge on billionaire wealth.

The difference matters because accumulated assets can be enormous even when yearly income is comparatively small. Under the proposed 5% rate, Sergey Brin's nearly $260 billion net worth could produce an estimated $13 billion bill. That calculation is based on wealth, not on how much income he received that year.

California billionaires paid about $4.1 billion in state income taxes last year, while their combined net worth was about $2 trillion. The comparison illustrates the different scales involved. Proposition 40 supporters see that asset base as a major funding source; opponents fear it could encourage relocation.