California Proposition 40 Targets Billionaires With 5% Wealth Tax

A one-time levy targeting California’s wealthiest residents has become the most consequential fiscal question on any state ballot in the country this election cycle. Proposition 40 would impose a 5% tax on the net worth of individuals who held more than $1 billion in covered assets and maintained California residency as of Jan. 1, 2026.

The measure attempts to close a window that proponents say ultra-wealthy taxpayers have already begun exploiting. By anchoring liability to a specific date at the start of the year, drafters aimed to prevent billionaires from relocating their primary residences to zero-income-tax states such as Texas, Nevada, or Florida before the vote. That retroactive trigger is legally unprecedented for a state-level wealth assessment and guarantees litigation if voters approve the initiative.

Ninety percent of collected revenue would be directed toward healthcare programs, according to the state Legislative Analyst’s Office. The remaining funds would cover administrative costs and education initiatives. The LAO estimates the tax could generate tens of billions of dollars over several years, though collection would likely stretch across multiple tax cycles due to the illiquid nature of many billionaire portfolios.

Arthur Laffer, the economist who designed the supply-side framework used during the Reagan administration, warned that the measure fundamentally alters the calculus for building large fortunes inside the state. Speaking during an appearance on Fox Business, Laffer argued that while California’s existing top marginal income tax rate of 13.3% — the highest in the nation — has historically failed to drive away the ultra-rich because it primarily targets earned income rather than accumulated equity, a direct hit on net worth changes the equation entirely.

“No one would want to go there to build their wealth only to be faced with this type of tax,” Laffer said, characterizing the proposition as a mechanism that would “destroy California.” He invoked historical precedents, noting that broad-based wealth taxes attempted in Europe largely collapsed under administrative burdens and capital flight.

Laffer’s assessment aligns with the trajectory of similar policies abroad. France implemented a solidarity tax on wealth in 1989 but repealed it in 2017 after government data showed an estimated 42,000 millionaires had relocated, costing the French treasury more in lost income and consumption taxes than the wealth levy generated. Spain recently introduced a temporary solidarity tax on high-net-worth individuals, which several regional governments are actively challenging in court.

Vermont Sen. Bernie Sanders has publicly backed the California effort, framing it as a necessary intervention to fund public health infrastructure. Proponents argue that extreme wealth concentration justifies extraordinary revenue measures, particularly when unrealized capital gains — the primary driver of billionaire net worth — escape traditional income taxation until assets are sold.

Valuing those unsold assets presents the steepest logistical hurdle. Real estate, pensions, and retirement accounts are generally excluded from the Proposition 40 calculation. However, privately held businesses, venture capital stakes, art collections, and complex trust structures lack daily market pricing. The California Franchise Tax Board, which would oversee enforcement, currently manages roughly 18 million personal income tax returns annually but has no existing apparatus for appraising bespoke billionaire asset portfolios.

The LAO projects that behavioral responses, including some departures, could reduce the state’s baseline income-tax revenue by less than $1 billion annually. That estimate assumes a relatively contained exodus. Critics counter that losing even a fraction of California’s roughly 200 billionaires would disproportionately damage state coffers, given that the top 1% of earners currently account for nearly half of all personal income tax receipts.

Supporters of the measure have mounted visible campaigns across the state, with signage appearing in major metropolitan areas drawing sharp debate over the economic fallout versus the potential healthcare funding windfall.

Proposition 40 remains pending voter approval in the upcoming election, with early polling indicating deep partisan divides over whether the state should test a policy mechanism that no U.S. jurisdiction has successfully sustained.