Building a Better California’s receipts reached about $318 million by Oct. 13, Bloomberg reported. The outlet said most had already been spent on the campaign to defeat Proposition 40. The measure would impose a tax on the wealth of some of California’s richest residents.
The Associated Press reported Oct. 9 that opposition fundraising exceeded $300 million, with Google co-founder Sergey Brin contributing close to one-third of that amount. State records show a narrower total: California Secretary of State data list $99,596,279 in contributions to committees formed to oppose Proposition 40 through Oct. 6. The figures cover different reporting categories, including one group’s receipts, an overall opposition tally and contributions to specific committees.
Under the proposal, people with net worth above $1 billion who were California residents on Jan. 1, 2026, would face a one-time levy of 5% of their net worth. The California Legislative Analyst’s Office (LAO) describes the affected population as a few hundred people.
The state voter guide allocates 90% of the revenue to health care. The remaining share could go to food assistance, education programs or administration of the tax.
The LAO estimates the tax could generate tens of billions of dollars over several years. It also says state income-tax revenue from billionaires could decline by less than $1 billion annually if they change their behavior in response to the measure.
California voters will decide Proposition 40 on Nov. 3, 2026.
