California’s Billionaire Tax Is Headed to the Ballot: The Real Battle May Be Over Valuation
Author: Redwood Valuation Content Team
Published: June 29, 2026
A high-profile political fight has now qualified for California’s November ballot. For the roughly 200 people it targets, and the advisors around them, the hardest question isn’t political. It’s how you put a defensible number on illiquid, complex wealth.
On June 25, 2026, the deadline passed for the union behind California’s proposed billionaire tax to pull or amend its measure, and it did neither. With that, the initiative is set to go before voters on November 3, 2026. The Service Employees International Union–United Healthcare Workers West (SEIU-UHW), which authored the measure, had spent weeks negotiating an off-ramp. Days before the deadline, it offered to abandon its one-time 5% wealth tax if Governor Gavin Newsom would champion a smaller 2% levy through the legislature instead. Newsom rejected the offer, and no legislative deal materialized before the cutoff [1]. The compromise window closed, the union let the deadline run, and the measure was certified for the ballot [2].
The result is a rare, high-stakes referendum on taxing wealth itself, not income, in the state that is home to more billionaires than any other [3]. The politics have drawn in a governor, a union, a U.S. senator, and some of the wealthiest people in the world. But beneath the headlines sits a quieter, more technical problem that will determine what the tax actually collects from any given taxpayer: valuation. That is where this conversation ultimately lands, and where it matters most to the people who would have to comply. It is also where timing becomes critical, the pool of valuation providers who truly understand illiquid assets and the mechanics of this measure is small, and the window to value those assets before any filing deadline is finite.
What the Measure Would Do
If voters approve it, the 2026 Billionaire Tax Act would impose a one-time tax of up to 5% on the net worth of California-resident individuals and certain trusts with a net worth of $1 billion or more. For taxpayers subject to the full tax, the 5% rate applies to their entire net worth, not only the portion above $1 billion, with a phase-down for individuals (not trusts) whose net worth falls between $1 billion and $1.1 billion [4]. The union estimates the levy could raise roughly $100 billion over five years, with most of the proceeds earmarked to offset federal healthcare funding cuts signed into law last year [5].
Two dates anchor the mechanics. January 1, 2026, is the tax obligation date, used to determine California residency for purposes of the measure. December 31, 2026, is the valuation date, used to measure net worth. The tax reaches broadly across personal property and wealth, stock, bonds, debt instruments, private business interests, intellectual property, art, and collectibles, while excluding directly held real property and certain qualified pensions and retirement accounts. Interests in entities that own real estate, however, may still require valuation under the broader business-entity rules[6].
Who’s For It, Who’s Against It, and Why
The measure cleared the signature threshold decisively, with the state verifying roughly 980,000 valid signatures against an 875,000 requirement [7]. Public polling has consistently shown majority support, though not by overwhelming margins. A Public Policy Institute of California survey conducted May 14–18, 2026 found 54% of likely voters would support the one-time tax of up to 5% on taxpayers with assets over $1 billion, with backing concentrated among Democrats (76%), voters aged 18 to 34 (75%), and renters (71%), while Republicans opposed it 82% and independents, homeowners, and older voters were split. An earlier Berkeley IGS poll (March 9–15, 2026) found voters favoring the measure 52% to 33%, with 15% undecided [8]. Those margins suggest real but soft support , the kind that a well-funded opposition campaign could erode before November. Its backers frame it as an urgent fix: in a statement accompanying their compromise offer, the proposal’s sponsors said they were willing to accept a smaller tax “because the crisis is immediate, the timeline is tight, and California needs guaranteed funding now” [9]. Senator Bernie Sanders traveled to California in the spring to rally support [10].
What makes the fight unusual is that some of the loudest opposition comes from the political left. Governor Newsom, a Democrat, is among the most prominent opponents. A spokeswoman said he “has been clear that he is strongly opposed to a California-only wealth tax,” arguing the measure “will defund teachers, schools, clinics, and public safety” and that “changing the tax rate doesn’t change this measure’s fundamental flaws”[11]. Newsom has warned the tax could deter investment and drive off the state’s largest taxpayers. Xavier Becerra, who finished first in this year’s open primary and is viewed as a possible successor, also opposes it [12].
California’s labor movement has fractured over the proposal as well. An unlikely coalition, including the California Teachers Association, Planned Parenthood Affiliates of California, and the California Medical Association, which represents more than 50,000 physicians, has formed to oppose it [13]. Their central argument echoes Newsom’s: that the windfall could be gradually offset by lost revenue as billionaires leave the state [14].
The wealthy residents in the crosshairs are mobilizing too. Building a Better California, a group funded by a coalition that includes Google co-founder Sergey Brin, has reportedly raised more than $100 million to oppose the tax and advance competing measures; a separate PAC backed by Ripple executive chairman Chris Larsen has spent millions more [15]. The coalition has advanced competing ballot measures aimed at curbing the tax, including a proposed constitutional amendment to bar retroactive taxation, a measure to keep new taxes from circumventing education-spending rules, and one to require additional audits of special taxes. Two of those counter-measures have qualified for the November ballot, setting up a direct clash with the billionaire tax [16].
That last front, retroactivity, points to the open legal question hanging over the whole exercise. A one-time tax measured on a single date, applied to wealth accumulated over decades, invites constitutional and administrative challenges over residency standards, retroactive application, and the taxation of non-public assets. The initiative itself anticipates this, building in an expedited review process for facial challenges, with validation actions required within 60 days of voter approval and a stated goal of resolving trial-level review by April 1, 2027 [17]. In other words, even passage in November would not be the end of the story.
Why Valuation Is the Hardest Part
Here is the part that gets less attention than the political drama but matters far more to anyone who would actually owe the tax. The headline is simple: measure net worth, apply a rate of up to 5%. In practice, “net worth” is anything but simple when a taxpayer’s wealth sits in private company equity, preferred shares, carried interests, non-public debt, trusts, intellectual property, collectibles, and other illiquid holdings.
For advisors, valuation is not a back-office detail; it could drive threshold determinations, the size of the tax, deferral eligibility, audit exposure, and disputes. The core question is whether the value assigned to a taxpayer’s ownership interest reflects the real economics of that interest, or whether a simplified, company-level rule produces a number that diverges sharply from what the taxpayer actually owns. Four features of the measure make that question especially live.
1. A formula-driven default that may not fit real capital structures
For interests in business entities other than publicly traded assets and sole proprietorships, the proposal establishes a presumptive valuation framework. The taxpayer must report the entity’s ownership percentage, book value, and book profits. The presumed value generally equals the entity’s GAAP book value, plus 7.5 times average annual GAAP book profits over the current tax year and the prior two tax years, if available, multiplied by the taxpayer’s ownership percentage. If average book profits are negative, they are treated as zero. A certified appraisal may be used instead if the taxpayer or the Franchise Tax Board demonstrates, by clear and convincing evidence, that the presumptive method would substantially overstate or understate the actual value of the business interest or the taxpayer’s ownership percentage [18]. That is a demanding standard, and it puts a premium on rigorous, defensible appraisal work.
The deeper issue is that a value for the business entity as a whole does not tell you the value of a specific ownership interest within it. Many venture-backed companies have layered capital structures: later investors hold senior preferred shares with liquidation preferences, while founders, employees, and earlier investors hold junior preferred or common stock. A simple per-share allocation can badly misstate economic value.
Consider a hypothetical company valued at $1 billion with 100 million shares outstanding, where a taxpayer owns 20 million Series C shares. Suppose the company also has Series D shares, senior to everything else, entitled to the first $1 billion of proceeds in a sale. In a simplified immediate-liquidity scenario, a $1 billion sale would send all proceeds to the Series D holders; the Series C shares would receive $0. But a naive pro-rata calculation tells a very different story:
$1 billion ÷ 100 million shares = $10 per share; $10 × 20 million Series C shares = $200 million; a 5% tax on $200 million = up to $10 million.
That approach would impose up to $10 million of tax on an interest that would yield nothing in a $1 billion sale. Real-world valuations weigh probabilities, timing, optionality, and security-specific rights. Junior shares may retain meaningful option value even when current liquidation proceeds are exhausted by senior preferences, but the example illustrates the central tension: a rule built for administrative simplicity can collide with the economic reality of how private companies are capitalized.
2. A recent-financing-round “floor” that can overstate junior interests
The proposal also states that a business entity’s value may not be less than the valuation implied by a funding round or other equity sale within two years of the valuation date, unless the taxpayer can show, by clear and convincing evidence, that the round would significantly overstate value [19]. That provision operates as a floor on the value of the entity, not as conclusive evidence of the value of any particular security.
The distinction is critical. A financing round prices one class of shares, often carrying liquidation preferences, downside protection, redemption rights, and other negotiated terms that common and earlier preferred shares don’t have. A senior preferred round can imply a headline valuation that overstates the worth of junior interests, particularly when liquidation preferences are large relative to enterprise value. This is the same reason valuation professionals routinely rely on option-pricing models, probability-weighted expected return methods, and other allocation techniques to value common stock. A company-level floor does not resolve how enterprise value should be allocated across share classes with different economic rights.
3. Tax due on value, even without cash to pay it
The measure recognizes that some wealth is illiquid. It includes an Optional Deferral Account (ODA) for qualifying liquidity-constrained taxpayers, broadly, those whose additional tax would exceed the value of their publicly traded assets. The ODA carries ongoing reporting obligations and remains binding until the taxpayer, estate, or assigns reconciles and closes it [20]. Even so, valuation and liquidity remain distinct problems. A taxpayer can owe tax based on an appraised or formula-driven value while holding no cash from the asset itself, a mismatch that hits private company founders, early investors, fund principals, and trust beneficiaries hardest.
4. Certified appraisals as a high-stakes compliance tool
The initiative gives certified appraisals a central role. For certain asset categories, taxpayers may need fair-market-value support, and the Franchise Tax Board would be authorized to issue guidance on appraisal requirements. The measure also allows penalties against appraisers for substantial or gross valuation misstatements, capped at 2% or 4% of the tax understatement, depending on severity [21]. The practical effect is a higher-stakes environment for valuation work. Appraisals will need to be contemporaneous, thoroughly documented, and capable of addressing both the statutory default rules and the economic substance of the asset, which, for a private company interest, means engaging with the capitalization table, recent financings, liquidation preferences, control rights, transfer restrictions, operating performance, and market conditions.
Why the Numbers Are So Uncertain
The state’s own analysts underscore how much rides on these valuation judgments. The Legislative Analyst’s Office and Department of Finance estimated the measure would likely produce a temporary revenue increase totaling tens of billions of dollars over several years beginning in 2027, while cautioning that the exact figure is hard to predict because billionaire behavior, asset values, and stock prices all move. They also flagged a likely ongoing decrease in state income tax revenue, hundreds of millions of dollars or more per year, if some billionaires leave the state [22]. A tax base built on volatile, often illiquid asset values is inherently more subjective than income tax reporting, which is precisely why the valuation question sits at the center of everything.
What Affected Taxpayers and Advisors Should Be Doing Now
The measure still must win at the ballot, survive likely litigation, and clear regulatory implementation. But the valuation issues it raises don’t wait for those outcomes. Advisors to potentially affected taxpayers should begin pressure-testing several areas:
Engage a qualified valuation provider early: the universe of appraisers who genuinely understand both illiquid, complex assets and the specifics of this measure is small. If the tax passes, hundreds of taxpayers would need sophisticated valuations within the same finite window ahead of the filing deadline, and demand could quickly outstrip capacity. Waiting to engage risks landing on a waitlist and a last-minute scramble, precisely when there is the least room for error.
Residency posture: with January 1, 2026, as the obligation date, residency analysis will be fact-specific for taxpayers with homes, businesses, and family ties across multiple states.
Asset inventory: taxpayers near or above the threshold need a detailed accounting of public and private holdings, liabilities, trust and entity interests, intellectual property, and receivables.
Private company capital structure: the key question is whether an interest is valued by its actual rights, or by a simple pro-rata share of enterprise value.
Recent financings: a round within two years of the valuation date may become a significant reference point, especially where it implies a high headline number.
Appraisal readiness: certified appraisals may be central to documenting value, supporting discounts, and responding to any FTB review under a clear-and-convincing-evidence standard.
Liquidity planning: taxpayers with concentrated illiquid holdings should evaluate whether the ODA provisions apply and what obligations would follow.
The Bottom Line
California’s 2026 Billionaire Tax Act is framed as a narrow, one-time levy on a small group of ultra-high-net-worth residents. The political fight, governor against union, billionaires against ballot measure, labor against labor, will dominate the headlines through November. But for the people who would actually have to comply, the decisive issue is valuation: the measure could require them to value complex, illiquid ownership interests under rules that may not align with the economics of private company ownership, and to defend those values against a demanding evidentiary standard.
If the measure advances, valuation support will be central to compliance, planning, and dispute resolution, and the work is far better done before the proposal’s status is resolved than under deadline pressure afterward.
Redwood Valuation provides valuation services for complex ownership interests and non-public assets, private company equity across share classes, carried interests, trust interests, and other illiquid holdings, built for tax, audit, transaction, and dispute contexts. If you advise clients who could be affected by the billionaire tax, contact Redwood early, before the rush, to discuss their valuation needs and secure capacity while there is still time to do the work right.
Citations
[1] Paul Kiernan, “Proposed California Billionaire Tax Clears Key Hurdle on Way to Ballot,” The Wall Street Journal, June 18, 2026.
[2] “California’s billionaire tax is headed to voters, and so are the measures to kill it,” The San Francisco Standard, June 25, 2026; “California billionaire tax qualifies for November ballot,” CalMatters, June 2026.
[3] Paul Kiernan and Laura J. Nelson, “Union Behind California Billionaire’s Tax Offers to Drop It in Favor of Smaller Tax,” The Wall Street Journal, updated June 18, 2026 (print ed. June 20, 2026).
[4] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[5] Paul Kiernan, “Proposed California Billionaire Tax Clears Key Hurdle on Way to Ballot,” The Wall Street Journal, June 18, 2026.
[6] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[7] Paul Kiernan, “Proposed California Billionaire Tax Clears Key Hurdle on Way to Ballot,” The Wall Street Journal, June 18, 2026.
[8] Public Policy Institute of California, “Californians and Their Government,” statewide survey, May 14–18, 2026 (986 likely voters, ±4.1%); Berkeley Institute of Governmental Studies (IGS) Poll, fielded March 9–15, 2026.
[9] Paul Kiernan and Laura J. Nelson, “Union Behind California Billionaire’s Tax Offers to Drop It in Favor of Smaller Tax,” The Wall Street Journal, updated June 18, 2026 (print ed. June 20, 2026).
[10] Paul Kiernan, “Proposed California Billionaire Tax Clears Key Hurdle on Way to Ballot,” The Wall Street Journal, June 18, 2026.
[11] Paul Kiernan and Laura J. Nelson, “Union Behind California Billionaire’s Tax Offers to Drop It in Favor of Smaller Tax,” The Wall Street Journal, updated June 18, 2026 (print ed. June 20, 2026).
[12] Paul Kiernan, “Proposed California Billionaire Tax Clears Key Hurdle on Way to Ballot,” The Wall Street Journal, June 18, 2026.
[13] Paul Kiernan and Laura J. Nelson, “Union Behind California Billionaire’s Tax Offers to Drop It in Favor of Smaller Tax,” The Wall Street Journal, updated June 18, 2026 (print ed. June 20, 2026).
[14] Paul Kiernan, “Proposed California Billionaire Tax Clears Key Hurdle on Way to Ballot,” The Wall Street Journal, June 18, 2026.
[15] “California’s billionaire tax is headed to voters , and so are the measures to kill it,” The San Francisco Standard, June 25, 2026; “California billionaire tax qualifies for November ballot,” CalMatters, June 2026.
[16] “California’s billionaire tax is headed to voters , and so are the measures to kill it,” The San Francisco Standard, June 25, 2026; “California billionaire tax qualifies for November ballot,” CalMatters, June 2026.
[17] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[18] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[19] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[20] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[21] State of California, Office of the Attorney General, Initiative No. 25-0024, Amendment No. 1: The 2026 Billionaire Tax Act, filed November 26, 2025.
[22] Legislative Analyst’s Office and California Department of Finance, fiscal analysis letter to Attorney General Rob Bonta regarding A.G. File No. 25-0024, Amendment No. 1, December 11, 2025.