The California Billionaire Tax Act crossed the 874,641-signature threshold to qualify for the November ballot, state officials announced Wednesday, advancing a proposal that has become one of the state’s most contentious political fights of the year.

The measure, known colloquially as the billionaire tax, would levy a one-time 5% wealth tax on any California resident whose net worth exceeds $1 billion. The Service Employees International Union-United Healthcare Workers West is backing the proposal, framing it as a way to fund California’s strained healthcare and education systems by requiring the ultra-rich to pay more.

The groups backing the measure have until June 25 to decide whether to proceed with placing it on the ballot or to negotiate a deal with the state, according to officials.

The announcement intensifies a year-long battle that has pitted organized labor against Silicon Valley’s wealthiest figures. Google co-founder Sergey Brin has spent $82 million on efforts to defeat the tax, while joining other billionaires in declaring he would leave California if it passes. Google co-founder Larry Page has also made moves to sever ties with the state amid the push, the Guardian reported.

Other tech moguls opposing the tax include Palantir co-founder Peter Thiel, crypto billionaire Chris Larsen, and Ring founder James Siminoff, all of whom have made substantial political donations to groups fighting the measure.

Gov. Gavin Newsom has previously denounced the proposal. He told the New York Times earlier this year that he would “do what I have to do to protect the state” and claimed the tax would drive away businesses.

California has the most billionaires of any state, many of whom have seen their wealth grow during the AI boom.

MSI previously reported that the billionaires tax was on track to qualify for the ballot in April, as signature-gathering efforts gained momentum despite unified opposition from tech executives. The measure’s formal qualification Wednesday sets up a November vote on a policy that would make California the first state to impose a direct wealth tax on its richest residents.