Stripe’s Patrick Collison puts $33 million into the fight over Prop. 40

State filings show the Stripe chief executive has given about $33.2 million to the main committee opposing California’s billionaire tax, making him its fourth-largest donor with a week left before Election Day.

By Hollis Varga

Patrick Collison, the co-founder and chief executive of the payments company Stripe, has become one of the largest individual funders of the campaign against Proposition 40, California’s proposed one-time tax on billionaires.

Mr. Collison has given $33,169,794 to Building a Better California, the committee leading the opposition, in five contributions between January and Oct. 2, according to Secretary of State campaign filings as compiled by the CalAccess Runway database. His largest single contribution was about $11.2 million. A Capital & Main analysis of state records published Oct. 22 put his total at $33.2 million. (Capital & Main notes that SEIU, which backs the tax, is a financial supporter of the outlet.)

That makes him the committee’s fourth-largest donor, behind the Google co-founder Sergey Brin ($102 million), the former Google chief executive Eric Schmidt (about $40.2 million) and the Kleiner Perkins chairman John Doerr ($40 million), according to the same filings. Mr. Collison’s money accounts for about a tenth of the roughly $318 million the committee had reported receiving as of its Oct. 13 filing.

How the giving grew

The contributions started small by the standards of this race. The Irish Times reported in July that Mr. Collison had given $2 million in January and $5 million in March. The bulk of his giving came later, as the campaign’s spending accelerated through the fall; his most recent recorded contribution was on Oct. 2.

The filings list Mr. Collison as Stripe’s chief executive with a Redwood City address. Forbes lists his residence as San Francisco.

Outside the ballot fight, his only other state political giving this cycle is $1.49 million to California Back to Basics Supporting Matt Mahan for Governor 2026, an independent committee backing the San Jose mayor’s campaign, in March and April, according to the Runway compilation.

Mr. Collison has not publicly explained the contributions. When The Irish Times asked about them in July, Stripe did not respond.

Who he is

Mr. Collison, 37, an Irish citizen, built Stripe with his younger brother, John; the company’s U.S. headquarters are in the Bay Area. Private investors valued the company at $159 billion in February, according to Forbes, which estimated Mr. Collison’s net worth at $17.5 billion as of Oct. 26. He is also a co-founder of the Arc Institute, a biomedical research nonprofit in Palo Alto.

The Collison brothers appeared among the city’s leading fortunes in the Inquirer’s Oct. 23 survey of the 100 families who hold San Francisco’s wealth.

The committee and its argument

Building a Better California, formed this year, has raised more than $333 million in all, according to Capital & Main. Through Oct. 20, it had given $118.5 million to a committee opposing Proposition 40 and about $186 million to support Propositions 41 and 42, rival measures that could nullify the billionaire tax. It has also put $10 million behind Proposition 45 and $6 million behind Proposition 37.

The committee argues that the tax would drive companies and wealthy residents out of California and destabilize the state budget. “We’re standing with doctors, teachers, firefighters, Planned Parenthood, Gov. [Gavin] Newsom, and the many others who oppose Prop 40, because it will devastate the state’s budget, tax base, and economy, all while making the problem it claims to want to fix — healthcare funding — much worse,” Abby Lunardini, a spokeswoman, told Capital & Main.

In a separate statement reported by the Los Angeles Times, the committee pointed to the breadth of its coalition: “It’s rare for such a broad coalition to unite around any single cause in California, but it reflects the potentially devastating impact of this measure on healthcare, education, and our state’s economy.”

The other side

Proposition 40 would impose a one-time 5 percent tax on the net worth of billionaires who lived in California at the start of 2026. It was written by Service Employees International Union-United Healthcare Workers West, which says the money is needed to offset federal health care cuts in last year’s budget law. (The Inquirer’s Oct. 16 explainer covers the measure and its rivals in detail.)

The union has contributed nearly $32 million in support, according to Capital & Main. Supporters have raised about $34.3 million in all, according to the Los Angeles Times, which reported on Oct. 24 that more than $351 million had been raised across the fight, about 90 percent of it to defeat the tax. Supporters had $1.6 million on hand as of Oct. 17, the paper reported.

Suzanne Jimenez, the union’s chief of staff, told Capital & Main that the billionaires’ spending was “not surprising.” “It’s very disappointing that they’d go to these lengths and spend all of this money when really they could do the moral and ethical thing of being part of our social contract,” she said.

The measure has backing from the California Democratic Party, the California Federation of Labor Unions, Sen. Bernie Sanders and Rep. Ro Khanna. It is opposed by Gov. Gavin Newsom, who has called for a national wealth tax instead, by the candidates to succeed him Xavier Becerra, a Democrat, and Steve Hilton, a Republican, and by the California Teachers Association, the California Medical Association and Planned Parenthood Affiliates of California. Jodi Hicks, Planned Parenthood Affiliates’ chief executive, told the Times that her organization would support a national or a California wealth tax but is concerned about this measure’s effects on the state budget and health care.

Polling has been mixed. A mid-September survey by UC Berkeley’s Institute of Governmental Studies found 45 percent of likely voters in favor and 42 percent opposed; an NBC News poll in late September found 48 percent in favor and 38 percent opposed, Capital & Main reported.

Election Day is Nov. 3.