Google co-founder Sergey Brin has now poured $102 million into the fight against California’s proposed billionaire tax, a one-time 5% hit that could cost him roughly $13 billion if voters pass it in November.
Campaign filings show the Google co-founder has sent the money to Building a Better California, the PAC and advocacy group leading the opposition to Proposition 40 and pushing rival measures that could knock the tax out even if it wins, according to Fortune.
Opponents of the levy have raised more than $187 million. Brin is the single largest donor. Groups backing the tax have raised about $32 million.
Proposition 40 would slap a one-time 5% tax on the net worth of roughly 200 California billionaires, with residency pinned to January 1, 2026, so the ultra-rich cannot simply pack a moving truck after Election Day. Ninety percent of the money would go to the state’s health care programs.
The other 10% would go to education, food assistance, and administration. Fortune put Brin’s net worth near $260 billion, which is how the $13 billion exposure is calculated. Other tallies put the bill even higher.
The Gateway Pundit reported in April that Brin had already spent about $57 million and had warned, in a rare on-the-record statement, that California was drifting toward the system his family fled.
“I fled socialism with my family in 1979 and know the devastating, oppressive society it created in the Soviet Union,” Brin told The New York Times. “I don’t want California to end up in the same place.”
The California Legislative Analyst says billionaires who were California residents on January 1, 2026, would be subject to the tax, with payments due beginning in 2027. Taxpayers could spread the bill over several years, although doing so would increase the amount owed.
Brin’s fortune has recently been estimated at roughly $267 billion to $284 billion.
A straight 5% levy on approximately $267 billion would amount to around $13.3 BILLION. That is more than 130 times the $102 million Brin has poured into the political fight.
There is, however, an important wrinkle.
Brin reportedly moved his primary residence to Nevada before the January 1 cutoff.
The Los Angeles Times reported that Brin relocated to a $42 million property on the Nevada side of Lake Tahoe as California’s proposed wealth tax began sending shockwaves through Silicon Valley.
That means the frequently cited $13 billion figure is not necessarily an established tax liability.
If Proposition 40 passes, any effort to classify Brin as a California resident on the cutoff date could trigger a massive residency fight with state tax authorities and potentially years of litigation.
Bloomberg Tax reported in September that Brin and other billionaires who fled California before the cutoff could nevertheless face aggressive scrutiny from the California Franchise Tax Board over whether they actually severed enough ties with the state to establish residency elsewhere.
In other words: billions of dollars could ultimately hinge on where Sacramento says Brin really lived on one particular day.
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