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Thiel made the $3 million contribution on December 29 to the California Business Roundtable, a powerful Sacramento-based lobbying group that represents large employers and corporate interests. The donation is the first seven-figure check publicly tied to opposition to the billionaire tax proposal and Thiel’s largest disclosed political gift since the 2022 midterm elections, when he spent more than $35 million backing populist conservative candidates.​ The New York Times was first to report on the donation, citing a public disclosure.

While the money is not formally earmarked only for the wealth-tax fight, the Roundtable is expected to serve as a central vehicle for organizing and funding the business community’s push to defeat the measure. Rob Lapsley, the group’s president, has said he is actively courting deep-pocketed donors across the state as part of a broader effort to marshal corporate and elite support against the tax initiative and other proposals viewed as unfriendly to business.​

Inside California’s billionaire wealth tax

The proposed 2026 Billionaire Tax Act would levy a one-time 5% tax on the net worth of California residents whose wealth exceeds $1 billion, targeting assets such as privately held businesses, stocks, bonds, art, collectibles, and intellectual property rather than income. Real estate and certain pensions and retirement accounts would be excluded, but otherwise the measure is designed to capture a broad swath of financial and intangible holdings within ultra-wealthy portfolios.​

If approved by voters, the tax would apply to anyone who is a California resident or part-year resident as of January 1, 2026, with the bill calculated on asset values at the end of 2026 and payable beginning in 2027. Billionaires could choose to spread payments over five years, but would incur an extra 7.5% annual nondeductible charge on the unpaid balance, effectively raising the long-run cost for those who opt to defer.​

Billionaires weigh exit or resistance

News of the proposal has already prompted a wave of soul-searching—and anger—among California’s ultrawealthy, with some high-profile founders and investors exploring moves to other states or further reducing their ties to California. At least several billionaires have already left the state in recent years, and business leaders warn the tax could accelerate an exodus and sap the innovation ecosystem that underpins California’s tech economy.​

Thiel himself acquired a property in Miami years ago but remains deeply intertwined with Silicon Valley through his investments and board roles, and his donation signals a decision to fight the measure politically rather than simply watching from afar. He told Joe Rogan in 2023 that real estate prices in Miami were too expensive, in his opinion. Other tech figures, including investors like Chamath Palihapitiya and Bill Ackman, have publicly criticized the tax, arguing it would chill entrepreneurship and risk-taking in the state.​

A rare point of agreement with Newsom

In an unusual alignment, some billionaire donors and Democratic Gov. Gavin Newsom find themselves on the same side of this fight. Newsom has come out against the billionaire tax, branding it bad policy and warning that even floating the idea has already damaged California’s reputation among the global wealthy.​

The campaign over the tax is still in its early stages: backers must gather nearly 900,000 valid signatures to place the measure on the November ballot, setting up months of high-stakes organizing on both sides. Opponents predict that more than $75 million could ultimately be spent to defeat the initiative, with Thiel’s $3 million check serving as an opening salvo in what is likely to become one of 2026’s most closely watched economic battles.

For this story, Fortune journalists used generative AI as a research tool. An editor verified the accuracy of the information before publishing.