On May 4, 2026, the Washington Supreme Court issued a per curiam order denying the petition for a writ of mandamus in Heywood v. Hobbs, holding that ESSB 6346 falls within the article II, section 1 exception for laws necessary for the support of state government and is therefore not subject to referendum.
That's not a surprise. The legislature put a necessity clause in the bill on purpose. They saw this coming.
One thing the ruling did not do: decide whether the tax itself is constitutional. That question is alive in a separate lawsuit. For the doctrinal analysis of how that challenge looks under Quinn and Culliton, see our constitutional analysis post.
So now what
There's still a constitutional lawsuit — filed April 9 in Klickitat County by the Citizen Action Defense Fund, led by former AG Rob McKenna and former Supreme Court Justice Phil Talmadge. The theory is real: Washington's constitution has treated income as property since 1933, and progressive income taxes have been struck down on that basis. Ninety-three years of precedent.
But here's the thing about 93 years of precedent: the same court that just blocked the referendum is the court that will hear the constitutional challenge. That court already found a way to uphold the 2021 capital gains excise in Quinn. Reasonable practitioners disagree about how the constitutional challenge to ESSB 6346 comes out — the structural arguments are real — but a court that has been protective of recent Washington revenue measures is not obviously a friendly forum either.
I hope McKenna wins. I genuinely do. But I would not bet my tax planning on it.
The math on waiting
ESSB 6346 applies to tax years beginning in 2028. First annual returns are due in 2029. Estimated payments are not required before July 1, 2029.
If you're married, the hit is worse. Two spouses each earning $700K pay nothing individually. Combined, they owe tax on $400K of income — roughly $39,600 a year — for no reason other than being married. That marriage penalty is baked into the statute and nobody in Olympia is fixing it.
What I tell clients
Plan as if this tax is permanent. The referendum is gone. The lawsuit is a prayer. The planning window — 20 months — is real and it is shrinking.
If you haven't started, start now.
Have questions about how ESSB 6346 affects your situation? Reach out.
Ready to plan? Start with the guide.
I wrote the Washington State Tax Planning Guide for High Earners for founders, physicians, tech executives, law partners, and investors who need to understand how ESSB 6346 actually works before 2028. 84 pages, $49.99.
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