The proposed Washington state millionaires’ 9.9% income tax comes with residency rules. And some taxpayers will really want to understand those rules.
In effect—and this is intentionally a rough description—a resident pays the millionaires’ tax on their Washington taxable income in excess of $1,000,000. (The actual law as currently proposed is significantly more complicated; this description is only meant to orient the reader.)
A Term to Know Before You Look at Residency Rules
Before looking at the residency rules, you need to understand one term: domicile.
Domicile means the primary place you live and intend to live. If you work in Washington state, rent or own a home you live in, plug into the local community here, have children in school here, and generally organize your life around Washington, you are likely domiciled in Washington state. If you always plan to return to Washington state, you are likely domiciled in Washington state.
If you spend time in Washington state and also spend time in another state (for example, Florida or Arizona), your domicile is generally the state where you have the deepest roots and strongest connections. This determination is inherently fuzzy and fact‑specific. (Hopefully, the legislature will provide a clearer definition in the final bill.)
Here is the key takeaway: If you are domiciled in Washington state, you will usually pay the millionaires’ income tax. But domicile alone does not determine whether you pay the tax. The statute separately defines who is treated as a resident for millionaires‑tax purposes, and those residency rules can override domicile in limited circumstances.
The 30‑Day Residency Rule
The first residency concept to understand is the so‑called “30‑day rule.” The proposed statute provides that a “resident” includes an individual:
(i) Who is domiciled in this state during the taxable year, unless the individual (A) maintained no permanent place of abode in this state during the entire taxable year, (B) maintained a permanent place of abode outside of this state during the entire taxable year, and (C) spent in the aggregate not more than 30 days of the taxable year in this state.
This provision is easy to misread. The 30‑day rule is not what makes someone a resident. It is an exception that allows a Washington domiciliary to avoid being treated as a resident—but only if all three conditions are satisfied for the entire year.
Under this rule, even if you are domiciled in Washington state, you are not treated as a resident for millionaires‑tax purposes if:
- You did not maintain any permanent place of abode in Washington state at any point during the taxable year;
- You did maintain a permanent place of abode outside Washington state for the entire taxable year; and
- You were physically present in Washington state for 30 days or less during the year.
Think of this as a narrow “de minimis presence” exception. If you truly live somewhere else, have no place to live in Washington, and are only in the state briefly, the statute treats you as a nonresident—even if domicile might otherwise be arguable.
Important note: Nonresidents may still be subject to the millionaires’ tax on Washington‑source income. For example, a high‑income California resident who owns rental property located in Washington or an interest in a pass‑through business operating in Washington may owe millionaires’ tax on that Washington‑source income. But they would not be taxed on all of their income.
The 183‑Day Residency Rule
For individuals who are not domiciled in Washington state, a different residency rule applies: the 183‑day rule. The statute provides that a resident also includes an individual:
(ii) Who is not domiciled in this state during the taxable year, but maintained a place of abode and was physically present in this state for more than 183 days during the taxable year.
This rule generally targets seasonal or extended‑stay visitors. If someone is not domiciled in Washington but maintains a place of abode here and spends more than half the year in the state, the statute treats them as a resident for millionaires‑tax purposes.
Both elements matter. Physical presence alone is not enough. The individual must also maintain a place of abode in Washington during the year.
Clarification #1: Partial Days Count as Full Days
The statute includes an important clarification regarding day counting:
For purposes of this subsection, “day” means a calendar day or any portion of a calendar day.
This means partial days count as full days when applying both the 30‑day rule and the 183‑day rule. Days can add up faster than many people expect. For example, entering Washington late on a Friday and leaving early Monday morning can count as four days, even if you were physically present for less than 48 hours.
Clarification #2: Partial‑Year Residency
The statute also addresses how residency applies when a person is classified as a resident for only part of the year. It provides:
An individual who is a resident under subsection (a) is a resident for that portion of the taxable year in which the individual was domiciled in this state or maintained a place of abode in this state.
This rule does not change who is a resident. Instead, it limits how much of the year is treated as resident once residency is established.
For example:
• If a Washington domiciliary fails the 30‑day exception (for example, by spending more than 30 days in the state), the individual is treated as a resident only for the portion of the year during which they were domiciled in Washington or maintained a Washington place of abode.
• If a non‑domiciliary is classified as a resident under the 183‑day rule, they are treated as a resident only for the portion of the year during which they maintained a Washington place of abode.
This partial‑year rule provides a measure of fairness by preventing the statute from automatically treating someone as a resident for an entire year when their connection to Washington exists only for part of that year.
Additional Resources
Changing Your Washington State Residency or Domicile
Text of Proposed Washington State Income Tax Bill (as of February 10, 2026)
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