Google co-founder Sergey Brin has now spent more than $100 million opposing California’s proposed billionaire tax, according to TechCrunch. The latest contribution was another $20 million to Build a Better California, a group campaigning against the measure.
The proposal, known as Proposition 40, would impose a one-time 5% tax on the net worth of roughly 200 billionaires living in California. TechCrunch estimates that Brin, whose fortune is currently around $267 billion, could face a tax bill of approximately $13.3 billion if the measure passes.
That means Brin has already spent the equivalent of less than 1% of his potential tax liability trying to defeat the proposal. The campaign has become one of the clearest examples of how aggressively some of Silicon Valley’s wealthiest founders are responding to the possibility of a direct tax on billionaire wealth.
Brin is not alone. Other prominent technology investors and founders have either left California or increased their political activity as the proposal moves toward a vote. TechCrunch notes that Larry Page, Peter Thiel, and Travis Kalanick have already relocated from the state, while Mark Zuckerberg reportedly purchased a major property in Florida this year.
California Governor Gavin Newsom has also opposed the state-level billionaire tax, warning that it could encourage wealthy residents and businesses to leave California. Instead, he has argued for a nationwide approach that would prevent billionaires from simply changing states to avoid the levy.
The proposed tax is intended primarily to support California healthcare programs at a time when the state faces potential reductions in federal funding. Voters are expected to decide on the measure in November 2026.
The controversy highlights the growing political debate over how governments should tax extreme wealth. Supporters argue that billionaires should contribute more directly to public finances, while opponents warn that aggressive wealth taxes could accelerate capital flight and weaken states that rely heavily on wealthy taxpayers and technology businesses.
