Google co-founder Sergey Brin spends over $100m fighting California’s billionaire tax, sparks online debate

Google co-founder Sergey Brin's latest donation has reignited debate over billionaire wealth and taxes

Google co-founder Sergey Brin has found himself at the centre of a fresh online debate after his campaign spending against California’s proposed billionaire tax crossed the $100m mark.

Brin, one of the world’s wealthiest technology figures, has donated another $20m to Build a Better California, an organisation campaigning against Proposition 40. The latest filing means Brin has now committed more than $100m towards efforts opposing the proposed tax, according to TechCrunch.

The figure has attracted attention because of the enormous amount involved and the size of the potential tax bill facing Brin if the measure becomes law. His estimated tax exposure has been put at around $13.3bn, while his fortune is estimated at roughly $267bn.

Proposition 40 proposes a one-time 5% tax on the net worth of approximately 200 billionaires living in California. The measure is designed to generate money for healthcare programmes in the state, with supporters arguing that the wealth of California’s richest residents could help offset serious funding pressures.

Brin’s spending has consequently become a focal point in the wider public argument over whether billionaires should be expected to contribute a larger share of their wealth towards public services. Online discussion surrounding the billionaire tax has reflected the divide, with Brin’s enormous campaign expenditure becoming an especially striking part of the debate.

The controversy also comes as several prominent technology billionaires have been linked to efforts to reduce their financial or personal ties to California. Google co-founder Larry Page, former Uber chief executive Travis Kalanick and venture capitalist Peter Thiel have all been reported as having left or reduced their connections to the state amid the broader wealth tax debate.

Meta founder Mark Zuckerberg has also reportedly purchased a $170m property near Miami, adding fuel to speculation about wealthy technology figures reconsidering California as a long-term base.

California Governor Gavin Newsom has opposed Proposition 40, arguing that a wealth tax could encourage billionaires to leave the state and potentially hurt California’s economy. Newsom has instead advocated for a national billionaire tax.

The debate has also produced an unexpected contrast within Silicon Valley. Nvidia co-founder and chief executive Jensen Huang has said he is comfortable with the proposed tax despite estimates that he could face a bill of around $8bn.

"I have not even thought about it once," Huang said in a January interview with Bloomberg. "We chose to live in Silicon Valley, and whatever taxes they would like to apply, so be it. I’m perfectly fine with it."

Brin’s position has therefore become particularly eye-catching because of the scale of his spending. Earlier in 2026, reports showed that he had already contributed tens of millions of dollars towards the fight against the proposed tax, making his latest $20m contribution another major development.

The issue is now heading towards a decisive moment. California voters are expected to decide on Proposition 40 in November. Until then, the battle is likely to remain a highly visible clash between wealthy technology figures, labour groups, politicians and voters over how much of California’s enormous private wealth should be directed towards public programmes.

For Brin, the argument has already become an unusually expensive political fight, with more than $100m now spent trying to stop a tax that could potentially cost him billions.