Updated July 29, 2026. Quick answer: RCW 26.16.030 defines community property as property acquired “after marriage or after registration of a state registered domestic partnership by either domestic partner or either husband or wife or both.” Washington is the only one of the nine whose community property statute names registered domestic partners in its own text.
What the wording does
Most community property statutes speak only of spouses or of marriage. Washington’s names both relationships in the operative sentence, so registration triggers the community property regime the same way marriage does.
State classification and federal tax treatment are two separate questions, and this is where they can come apart. Whether a relationship is recognised for federal purposes governs whether federal provisions that turn on marriage apply — including the basis rule at the heart of this. State law classifies the property; federal law decides what follows. If you are in a registered domestic partnership rather than a marriage, that is a question for an adviser who can look at your actual filing status, not something to infer from the state statute.
Why the difference is worth knowing rather than trivia. Community property classification decides what happens to basis at the first death — IRC §1014(b)(6) gives BOTH halves a new basis, where a common-law state gives only one. So which assets are classified as community, and from what date, decides how much of that benefit you actually get.
The practical read
For a married couple in Washington the statute behaves like the other eight. The distinctive language matters for partners who registered rather than married — a population most community property writing simply does not address, and one where the state answer and the federal answer may genuinely differ.
Sources
Each state’s own codified statute as quoted on this page. The nine-state list and the federal treatment are per IRS Publication 555 and Internal Revenue Manual 25.18.1.2.3. IRC §1014(b)(6) for the basis consequence. All read July 2026.
This states what the cited authority says. It is not tax advice, and retirement-plan design turns on facts about your business and your other entities that no page can see. Every dollar limit referenced here is indexed and changes annually.