California's proposed 'Billionaire Tax' could reshape wealth planning for ultra-high-net-worth clients

A new proposal from Jim Mangia,  president and CEO of St. John’s Community Health, has been filed with the California Attorney General this week. It seeks to place a sweeping one-time “Billionaire Tax” on the state’s 2026 ballot—an initiative that, if approved, could significantly alter the financial calculus for the state’s wealthiest residents and their advisors.

The proposed measure, titled the 2026 Billionaire Tax Act, would impose a 5 percent levy on the net worth of individuals whose total assets exceed $1 billion as of December 31, 2026. It was submitted by Mangia (who referred to the hike as 'modestly increasing' taxes) and Suzanne Jimenez through the Kaufman Legal Group in Los Angeles. The Attorney General’s office will now prepare a title and summary before the measure’s backers can begin collecting the nearly 875,000 signatures required to qualify for the November 2026 ballot.

A new phase in California’s wealth taxation debate

The measure positions itself as a response to projected federal funding shortfalls for Medi-Cal and other social programs, claiming that California faces roughly $30 billion in annual health care funding gaps. It proposes allocating 90 percent of the new revenue to health care and 10 percent to K–12 public education, capped at $25 billion per year through a separate “Billionaire Tax Reserve Account.”

The initiative argues that billionaires’ wealth “has largely escaped fair taxation” and points to what it describes as a widening gulf between the accumulation of extreme wealth and the state’s fiscal capacity. Under the plan, the Franchise Tax Board would require all California residents to declare their total net worth, including interests in private companies, real estate, art, and intellectual property. The tax could be paid in full or spread over five years with interest, with steep penalties for underreporting.

Who it could affect

Although Tesla founder Elon Musk relocated to Texas in 2020, many of the world’s wealthiest individuals continue to call California home. Among those potentially affected by the proposed measure are:

• Larry Page and Sergey Brin, co-founders of Google, with estimated net worths of about $130 billion and $125 billion, respectively.
• Mark Zuckerberg, CEO of Meta Platforms, worth roughly $115 billion.
• Larry Ellison, Oracle co-founder, with assets around $140 billion, though he now primarily resides in Hawaii.
• Eric Schmidt, former Google CEO, with an estimated $25 billion.
• Reed Hastings, Netflix co-founder, at about $6 billion.
• Patrick and John Collison, Stripe founders, each estimated near $10 billion.

In total, California is home to around 180 billionaires, according to Forbes and Bloomberg data, together holding roughly $2 trillion in wealth.

Wealth management and estate planning implications

For financial planners and private wealth advisors, the proposed wealth tax represents a significant policy shift with practical and strategic consequences. Unlike income-based taxation, the levy would be assessed on unrealized gains and asset values, introducing complex valuation, liquidity, and compliance challenges.

Family offices and advisors would need to determine accurate fair market values across a broad mix of asset classes, including privately held businesses, venture capital holdings, and trust structures. The bill allows for “optional deferral accounts” for taxpayers with illiquid portfolios, but any deferred amounts would accrue interest, potentially eroding long-term net worth.

Advisors are likely to explore strategies around asset location, interstate domicile, and the timing of liquidity events. Residency planning could re-emerge as a core advisory issue, as high-net-worth individuals weigh the financial implications of maintaining California residency against relocation to lower-tax states such as Texas, Florida, or Nevada.

Broader policy and behavioral effects

If passed, California would become the first U.S. state to tax net wealth directly, setting a precedent that could ripple through fiscal policy debates nationwide. Supporters argue that the one-time tax is modest relative to billionaires’ asset growth and necessary to protect state-funded programs from federal cuts. Critics are expected to warn of capital flight, investment retrenchment, and longer-term damage to the state’s entrepreneurial ecosystem.

For advisors, the proposal underscores a growing emphasis on comprehensive balance sheet planning—integrating tax, estate, and liquidity considerations into multi-generational strategies. Even if the measure fails to reach the ballot, its emergence highlights an increasingly assertive approach to taxing extreme wealth, one that could influence future federal or state-level proposals.

The Attorney General’s office is expected to issue a formal summary within weeks. If approved for circulation, backers will have until spring 2026 to gather sufficient signatures to secure a place on the ballot.