Google co-founder Sergey Brin spends $102 million to stop California from taxing billionaires’ wealth

Google co-founder Sergey Brin has spent $102 million to oppose California’s proposed wealth tax on billionaires, after making another $20 million donation to the campaign fighting the tax, according to a report by Bloomberg.

Brin donated the additional $20 million to Building a Better California, according to a filing made public Friday. The group is mainly campaigning against Proposition 40, while also supporting pro-business policies, housing affordability measures and other issues.

Proposition 40, which will go before California voters in November, proposes a one-time 5% tax on the wealth of the state’s billionaires.

Building a Better California is also funding two competing ballot measures that could cancel the billionaire tax if they receive more votes than Proposition 40.

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Brin has emerged as the biggest financial backer of the campaign opposing the proposed tax. In comparison, the group supporting the wealth levy, which was launched by a healthcare workers union, has raised just over $30 million so far, according to campaign filings.

A spokesperson for Building a Better California declined to comment further.

Brin, the world’s fourth-richest person, has also been helping bring other tech billionaires into the fight against the proposed tax. His political spending in California has increased sharply in recent months.

He has also bought a $42 million mansion on the Nevada side of Lake Tahoe and now lists Nevada as his residence in state records.

Brin’s net worth is estimated at about $282 billion, according to the Bloomberg Billionaires Index.

Why is California proposing a billionaire tax?

California’s proposed billionaire tax is aimed at raising money for healthcare, education and food assistance at a time when the state is facing the impact of major federal healthcare funding cuts.

The measure was pushed by the Service Employees International Union-United Healthcare Workers West (SEIU-UHW), a healthcare workers union. The union says federal funding cuts could take around $100 billion away from California’s healthcare system over the next five years.

Under Proposition 40, billionaires who were California residents on January 1, 2026 would have to pay a one-time tax equal to 5% of their net worth. The tax would be due in 2027, although taxpayers could choose to spread the payment over five years at an additional cost.

The proposal is expected to affect roughly 200 billionaires and could raise about $100 billion, according to its supporters. The money would be placed in a special fund, with 90% going towards healthcare and the remaining 10% towards education and food assistance.