Proposition 40 on the Nov. 3 ballot would impose a one-time 5% tax on the wealth of California's billionaires, sending most of the money to health care. CalMatters estimates about 200 Californians who were worth more than $1 billion at the start of the year would owe the tax.

Why it matters: It is the most expensive and most fought-over measure on the state ballot, and two rival measures on the same ballot could cancel it out. See our full Election 2026 guide.

What it would do

According to the Legislative Analyst's Office, the tax applies to people who were California residents as of Jan. 1, 2026. It would be due in 2027, and taxpayers could choose to spread payments over five years at an extra cost. Real estate, pensions and retirement accounts are generally excluded from the calculation.

The LAO says 90% of the money would go to health care, with the rest for education, food assistance and administration. The revenue would be exempt from the Prop 98 school funding guarantee and the state spending limit.

How much money

The LAO estimates the measure would raise tens of billions of dollars over several years. It also warns of a possible ongoing loss of state income tax revenue of less than $1 billion a year if some wealthy residents leave, plus administrative costs that could reach tens of millions of dollars annually. Sponsor SEIU-UHW projects about $100 billion over five years, CalMatters reports.

The Prop 41 and 42 catch

CalMatters notes that Prop 40 would be nullified if Prop 41 or Prop 42 passes with more yes votes.

Who's for and against

Supporters include SEIU-UHW, Sen. Bernie Sanders, Teamsters California, AFSCME California, the California Democratic Party and the California Labor Federation. Opponents include the California Business Roundtable, the California Medical Association, the California Teachers Association, Planned Parenthood, California Professional Firefighters, the State Building and Construction Trades Council, Ripple co-founder Chris Larsen and investor Ron Conway.

The Sacramento Bee and San Diego Union-Tribune editorial boards support it; the Orange County Register and Los Angeles Times oppose it.