California’s Billionaire Tax Battle Intensifies as Voters Weigh Proposition 40

September 21, 2026 — California voters will decide whether to impose a one-time wealth tax on billionaires, setting up a major fight over healthcare funding, inequality, investment and the state’s economic future.

California voters are preparing for a consequential tax debate as Proposition 40 asks whether residents with more than $1 billion in covered assets should face a one-time wealth tax of up to 5%.

The measure will appear on the November 3 ballot and would apply to billionaires who were California residents on January 1, 2026, with payments generally beginning in 2027.

Unlike California’s existing income taxes, Proposition 40 would target accumulated wealth, including businesses, securities, art, collectibles and intellectual property, while generally excluding real estate, pensions and retirement accounts.

State analysts say 90% of the revenue would be reserved for public healthcare services, while the remaining funds would support education, food assistance and administration of the new tax.

California’s Legislative Analyst estimates the proposal could generate tens of billions of dollars over several years, though supporters have promoted a substantially higher figure of roughly $100 billion.

Supporters argue the money is needed to shore up healthcare programs and other services, framing the proposal as a way for ultrawealthy residents to contribute more toward statewide public needs.

Economist Emmanuel Saez, who helped develop the measure, argues California’s concentration of billionaire wealth makes the state uniquely positioned to test a tax aimed directly at large fortunes.

A 2026 research paper by Saez and fellow economists Jasper Boll and Gabriel Zucman estimated that California billionaires collectively held about $2.3 trillion in wealth by midyear.

Opponents counter that taxing wealth rather than income could encourage some wealthy residents to relocate, reduce investment or restructure their finances, potentially shrinking California’s future income-tax base.

The nonpartisan Legislative Analyst’s Office says behavioral responses could reduce ongoing state income-tax collections by less than $1 billion annually, even as the wealth tax produces substantial temporary revenue.

Governor Gavin Newsom opposes Proposition 40 and has argued that any wealth-tax approach would be better pursued nationally, rather than by a single state competing for businesses and high-income residents.

The campaign has attracted significant spending from both sides, including organized labor supporting the measure and business interests opposing it, making Proposition 40 one of California’s most closely watched initiatives.

Google co-founder Sergey Brin has emerged as a prominent opponent, with Reuters reporting that he has spent heavily against Proposition 40 and on competing measures that could effectively block it.

Polling suggests voters remain divided rather than settled. A September Public Policy Institute of California survey found 52% of likely voters supporting Proposition 40 and 46% opposing it.

An earlier Berkeley IGS Poll in August found 48% support and 41% opposition among likely voters, highlighting substantial uncertainty as campaigns intensify ahead of the November election.

Support varies sharply by party. PPIC found 72% of Democratic likely voters favored the measure, compared with 46% of independents and 21% of Republicans in its September survey.

The debate also reflects a broader national argument over taxing extreme wealth, with supporters emphasizing inequality and public revenue while critics focus on mobility, valuation difficulties and economic competitiveness.

California’s proposal differs from annual wealth taxes once used in several European countries because Proposition 40 is designed as a one-time levy tied to residency on a specific date.

Even if approved, implementation could prove complex because privately held businesses, intellectual property and other nonpublic assets must be valued, creating administrative challenges and likely disputes over assessments.

Ultimately, Proposition 40 gives Californians a direct choice over whether a temporary tax on billionaire wealth should finance public programs, while accepting the possible fiscal, legal and economic trade-offs involved.