Google cofounder Sergey Brin has emerged as the biggest donor opposing California’s proposed billionaire wealth tax, contribution $102 million to a political group fighting the measure that could leave him facing tax bill of about $13 billion if approved by voters. As per the campaign fillings, Brin has donated a teal of $102 million to building a Better California, a political action committee campaigning against California’s proposed wealth tax while supporting pro-business, housing and infrastructure policies. Opposition groups have collectively raised more than $187 million, compared with roughly $32 million raised by supporters of the measure.
The development was reported by Fortune, citing state financial campaign records. The contribution makes him the single largest founder of the anti-tax effort.
Brin now lists Nevada as his residence, according to state records, and reportedly bought a $51 million home near Miami Beach in March. His family office, Koop, was incorporated in Delaware in December 2025.
“I fled socialism with my family in 1979,” he told The New York Times in April, adding that he does not want California to end up in the same place. Former Google CEO Eric Schmidt and PayPal cofounder Peter Thiel have also donated to groups opposing the measure. Brin has likened the proposal to the socialist society he left behind. Some of the wealthy are shifting their holdings out of the state. Larry Page, Google’s other cofounder, has moved several assets out of California. Oceankind, the ocean science nonprofit founded by his wife, Lucy Southworth, was incorporated there around the same time.