California Proposition 40 puts fiscal trade-offs before voters

California Proposition 40 would impose a one-time 5% tax on the net worth of billionaires who were state residents on January 1, 2026, if voters approve it in November. The Legislative Analyst’s official assessment says the California proposition 40 wealth tax would probably generate tens of billions of dollars over several years, while also creating uncertain collection costs and possible future losses of income-tax revenue.

The measure is a proposed ballot initiative, rather than a recurring wealth tax already in force. It would be due in 2027, though taxpayers could pay over five years at an additional cost. Real estate, pensions and retirement accounts would generally be excluded, according to the official voter guide.

Ninety percent of the proceeds would be reserved for public health services. The remainder would fund education, food assistance and administration of the tax. Those earmarks frame the central choice for voters: temporary receipts for specified services against implementation and behavioural risks that cannot yet be measured precisely.

Would Proposition 40 harm California?

The available evidence does not establish a definite net harm. The Legislative Analyst projects a temporary increase in state revenue, but says the amount and timing would be difficult to forecast because much taxable wealth is tied to changing stock prices and taxpayers may take steps to reduce what they owe.

It also identifies a potential longer-term cost. Some affected taxpayers could change their behaviour, including by leaving California, and thereby reduce their state income-tax payments. The analyst estimates that such responses would probably cut continuing state revenue by less than $1 billion a year. That is a forecast, not an observed result.

California would also need to value and collect tax on a range of assets. CalMatters reports that the system could cover listed shares, investment accounts, private business interests, art, wine and vehicles. Experts cited by the publication differed over the difficulty: some said the Franchise Tax Board would require greater appraisal and audit capacity, while others said valuation techniques already used for other taxes could be adapted. The official analysis puts administrative and collection costs at tens of millions of dollars annually for several years, paid from the new revenue.

What could Proposition 40 raise?

A report written by several experts who helped draft the initiative estimates roughly $100 billion in revenue during 2027 through 2031, or about $20 billion a year, from 250 wealthy taxpayers. Its authors argue that the funds could support health care, K-14 education and food assistance amid federal funding pressures. The official analysis offers a more cautious range, saying collections would probably reach tens of billions without assigning a precise total.

Claims of a large billionaire migration remain unsettled. Economists cited by CalMatters said the proposal is unusual enough that there is no reliable way to determine whether it would prompt a broad departure. European wealth-tax experience is not directly comparable, they said, because those systems differed in their rates, duration and use of revenue.

The measure could also face legal and electoral obstacles. The California Budget & Policy Center says its attempt to tax individuals based on their residence at the start of 2026 would likely be challenged in court. Separately, the voter guide says Propositions 41 or 42 could prevent Proposition 40 from taking effect if either wins more yes votes and courts find the measures conflict.

This story draws on original reporting from Project Syndicate.