The California Budget & Policy Center has a new report, “Billionaire Tax Explained: What Proposition 40 Would Mean for California” (Aug. 2026). Here is the “key takeaway”:

Prop. 40 would institute a one-time 5% tax on the wealth of billionaires to raise tens of billions in temporary revenue to address the loss of federal funding and other threats to health, nutrition, and education services, largely a result of H.R. 1 — the 2025 budget reconciliation law known as the “One Big Beautiful Bill Act.” Prop. 40 could potentially raise tens of billions in revenue in the short-term to preserve critical services, but may also lead to some income tax revenue losses in future years to the extent that billionaires leave the state to avoid the tax.