Four Richest Californians Could Pay 40% of Proposed Wealth Tax as Billionaires Fund Opposition Drive

California's four richest billionaires could face a combined wealth tax liability of approximately $42.8 billion (£32.12 billion) under a proposal going before voters on 3 November.

Sergey Brin, Jensen Huang, Larry Page and Mark Zuckerberg account for about 40% of an estimated $107 billion total (£80.32 billion), according to a Los Angeles Times analysis. That projection draws on Forbes wealth estimates from 16 October, rather than official tax assessments.

Billionaire donors have meanwhile contributed $293 million (£219.96 million) to campaigns opposing the tax or supporting competing measures. The proposed one-off levy has become a costly political fight over California's healthcare funding and tax base.

Proposition 40 would charge qualifying billionaires 5% of their taxable net worth if they were California residents on 1 January 2026. Their wealth would be measured at the end of 2026, with payment due in 2027.

Taxpayers could pay over five years, but doing so would cost more. Real estate, pensions and retirement accounts would generally be exempt.

Four Technology Fortunes Dominate the Billionaire Tax Estimate

The four men's fortunes are closely tied to the stock they hold in major technology businesses. Brin and Page co-founded Google, Huang is Nvidia's chief executive and Zuckerberg leads Meta. Such holdings can gain billions in market value without producing corresponding taxable capital gains until shares are sold.

The $42.8 billion (£32.14 billion) figure is an approximate calculation from the reported 40% share.

Brin alone had an estimated net worth of $257.1 billion (£193.04 billion) on 16 October, according to the newspaper's Forbes-based analysis. Share prices, exemptions and residency determinations could affect any eventual tax bill. No tax has been assessed under the proposal.

The wider $107 billion (£80.34 billion) estimate draws on research by economists Jasper Boll, Emmanuel Saez and Gabriel Zucman, originally issued in May and revised in August.

Their study examines billionaire fortunes, tax payments and potential revenue. Saez and Zucman helped develop Proposition 40, a relevant consideration when comparing competing projections.

Billionaire Tax Opponents Put Millions Behind Rival Measures

Not all California billionaires have contributed to the campaign against the measure. The newspaper examined about 260 people identified using Forbes data and found that 30 billionaires, or their spouses, had contributed. That is approximately 12% of the group, and says nothing definitive about the views of the remainder.

The $293 million (£219.97 million) figure covers contributions opposing Proposition 40 and supporting Propositions 41 and 42, based on campaign records analysed through 16 October.

It is not a tally of spending solely against the billionaire tax. Brin contributed $102 million (£76.57 million), while former Google chief executive Eric Schmidt gave approximately $40.2 million (£30.17 million). Venture capitalist John Doerr contributed $40 million (£30.02 million).

Brin's contribution amounted to less than 1% of his potential tax bill under the newspaper's estimate. Ripple co-founder Chris Larsen personally contributed roughly $17.5 million (£13.13 million), with Ripple Labs adding another $5 million (£3.75 million).

Billionaire Tax Revenue Estimates Remain Disputed

Supporters argue the levy could help replace healthcare funding threatened by federal spending cuts. California's official voter guide says 90% of any revenue must support public healthcare services. The remainder would fund education, food assistance and administration.

Yet the estimated liability is not the same as money the state would ultimately collect. An October study by Hoover Institution researchers Benjamin Jaros and Joshua Rauh projects around $30 billion (£22.50 billion) in collections, within a range of $28 billion (£21.01 billion) to $36 billion (£27.01 billion).

Their model incorporates assumptions about residency, taxpayer departures and legal disputes. By contrast, California's nonpartisan Legislative Analyst's Office expects tens of billions in revenue but warns the amount is difficult to predict.

Governor Gavin Newsom opposes a California-only billionaire tax, arguing that it could encourage wealthy residents to move elsewhere. He has instead supported a nationwide minimum tax on billionaires.

Supporters of Proposition 40 include Senator Bernie Sanders and healthcare unions, while opponents include the California Teachers Association.

If voters approve Proposition 40 on 3 November, tax administrators would still need to establish who qualifies and calculate taxable wealth. Owning property outside California would not, on its own, settle a person's residency.

Courts could also become involved if competing Propositions 41 or 42 receive more Yes votes and are found to conflict with Proposition 40.

The outcome will determine whether California proceeds towards a new tax on billionaire wealth, but it will not settle the revenue question immediately. The projected liabilities, campaign contributions and competing collection estimates all rest on different calculations. Actual tax receipts, if any, would depend on the law taking effect and how it is administered.