Prenuptial Agreement Requirements in Washington

At a glance

Requirements one by one

Washington uses a writing statute plus case law

Washington has not adopted the UPAA or UPMAA. RCW 19.36.010 supplies the statute-of-frauds form rule for an agreement made upon consideration of marriage. Bernard and Matson provide the controlling two-prong fairness test.

RCW 26.16.120 is not the ordinary divorce-focused prenup statute. It concerns an agreement jointly made by people who are already spouses or domestic partners about community property, to take effect on death. Its deed-style formalities should not be imported into every premarital agreement.

The agreement must be written and signed by the charged party

RCW 19.36.010 makes a marriage-consideration agreement void unless the agreement or a memorandum is written and signed by the party to be charged. That is not a codified “both parties” UPAA sentence, although obtaining both signatures avoids one-sided enforceability questions.

The marriage is the consideration named by the statute and the event the premarital bargain contemplates. Washington's cases evaluate agreements made before the wedding and invoked after the marriage.

No notary, witnesses, or recording are universal prenup conditions

RCW 19.36.010 requires the signed writing; it does not add notarization, acknowledgment, witnesses, attestation, an oath, or recording. A real-property instrument used to carry out a term can have its own deed or recording rules.

The stricter witnessed-and-acknowledged form in RCW 26.16.120 belongs to the different spouses' community-property agreement that takes effect on death. It is not the ordinary premarital validity checklist.

Disclosure becomes decisive when the bargain is substantively unfair

Bernard first asks whether the agreement makes fair and reasonable provision for the spouse opposing enforcement. If it does, the analysis ends. If it does not, procedural fairness requires full disclosure of the amount, character, and value of the property involved.

Washington has no UPAA-style statute supplying a written waiver of further disclosure or an adequate-knowledge substitute. Knowledge of assets can be important evidence, but the controlling second prong is the case-law full- disclosure test.

Counsel and timing belong to the second prong

A substantively fair agreement does not automatically fail because one party lacked separate counsel. But a substantively unfair agreement must satisfy the procedural prong: free and voluntary execution on independent advice from counsel, with full knowledge of each spouse's rights.

Matson directs courts to examine bargaining position, sophistication, independent advice, understanding of legal consequences, and the timing of signing relative to the wedding. Washington sets no fixed number of review days. Matson invalidated an eve-of-wedding agreement where the opposing spouse had no reasonable opportunity to obtain meaningful independent advice.

Bernard preserves the two-prong execution-time test

The enforcement proponent bears the burden. A substantively fair and reasonable agreement is enforceable without reaching the procedural prong. A substantively unfair agreement can still be enforced only if full disclosure, independent advice, full knowledge, and voluntary execution establish procedural fairness.

Bernard refused to shift substantive fairness to the time of enforcement, stating that validity rests on circumstances surrounding execution. Washington therefore does not use a general changed-circumstances or later-hardship second look.

A maintenance waiver is part of the fairness analysis

Bernard considered a bargain that prevented one spouse from seeking spousal maintenance and treated that restriction as part of its conclusion that the agreement was substantively unfair. A support waiver is not automatically barred, but it must survive the same two-prong test as the rest of the agreement.

No Washington premarital statute provides a public-assistance eligibility override, and Bernard rejected a general enforcement-time unconscionability test.

Child support and parenting remain court-controlled

RCW 26.09.100 directs the court to order either or both parents to pay child support under the statewide support schedule after considering the relevant factors. A premarital bargain cannot replace that statutory judicial order.

For parenting, RCW 26.09.187 requires residential provisions consistent with statutory limitations and the child's relationships, development, needs, and best interests. The parties' agreements are factors only when knowing and voluntary; they do not conclusively dictate a future parenting plan.

A later amendment faces the same fairness review

Washington has no prenup-specific statutory amendment or revocation checklist. Bernard analyzed a prenup amended after marriage under the same two-prong framework and stated that postmarital amendment did not alter the analysis. A marriage-consideration change also must satisfy RCW 19.36.010's signed-writing rule as applicable.

RCW 26.16.120 separately allows its death-effective community-property agreement to be amended using the same deed-style formalities. That narrow route should not be described as the universal change method for an ordinary prenup.

What trips people up

• RCW 26.16.120 is a different instrument. It applies to spouses or domestic partners, community property, and effect upon death.
• Washington does not require both fairness prongs in every case. A substantively fair agreement ends the inquiry; procedural fairness is needed to save a substantively unfair agreement.
• Counsel has no fixed waiver form. Independent advice and meaningful time are fact-specific parts of the procedural test, not a UPAA checkbox.
• The test looks to execution. Bernard rejected a general enforcement-time fairness review.

Common questions

Is signing the night before the wedding automatically invalid?

No fixed day count creates automatic invalidity, but Matson shows that eve-of- wedding timing can defeat procedural fairness when the agreement is unfair and the opposing party lacks a reasonable opportunity for independent advice.

Who must prove enforceability?

Bernard states that the spouse seeking enforcement bears the burden under the two-prong test.

Can a later amendment cure an unfair original agreement?

Only if the amendment process itself cures the problem. Bernard held that a later amendment did not cure the original procedural defects where the allowed renegotiation was too limited, even though more time and counsel existed later.

Statutes and sources

• RCW 19.36.010(3) — signed-writing statute of frauds for an agreement made upon consideration of marriage. Official statute (accessed 2026-07-27).
• In re Marriage of Bernard, 165 Wn.2d 895 (2009) — current two-prong test, burden, execution-time fairness, maintenance treatment, and amendment review. Washington Supreme Court opinion (accessed 2026-07-27).
• In re Marriage of Matson, 107 Wn.2d 479 (1986) — procedural factors, disclosure, independent advice, understanding, and timing. Washington Supreme Court opinion (accessed 2026-07-27).
• RCW 26.16.120 — separate death-effective community-property agreement and its deed-style formalities. Official statute (accessed 2026-07-27).
• RCW 26.09.100 and RCW 26.09.187 — child-support order and parenting-plan factors. Official support statute and parenting statute (accessed 2026-07-27).