How Do I Enforce a Prenuptial Agreement?

By Chad Foster, Family Law Attorney · Updated July 16, 2026

A prenuptial agreement is not something you file at the courthouse the day you sign it. You enforce it when it actually matters, in the divorce, by presenting it to the court and asking the judge to hold both parties to its terms.

When and Where a Prenup Gets Enforced

A prenup sits quietly in the background for as long as a marriage lasts. It has no day to day effect. It becomes operative only when the marriage ends, most often in a divorce, and sometimes at the death of a spouse. In a divorce, the agreement comes into play as the court works out how to divide the couple's property and whether to award spousal support. The spouse who wants the agreement honored presents it to the court and asks the judge to apply its terms rather than the default community property rules.

That is the whole mechanism. There is no separate lawsuit to enforce a prenup and no advance approval process. It is raised inside the divorce case, and the court decides whether it is valid and, if so, applies it. Because Washington has no statute governing prenuptial agreements, whether the court enforces yours depends entirely on a body of case law built around fairness.

The Test the Court Applies

The controlling decision is In re Marriage of Matson, 107 Wn.2d 479 (1986). Matson set out a two part analysis that Washington courts still use to decide whether a prenup is enforceable.

The first part asks whether the agreement makes a fair and reasonable provision for the spouse who is not seeking to enforce it. In other words, the court looks at the substance of the deal. If the agreement is substantively fair, it generally passes, and the inquiry can end there. If the agreement is not fair, that does not automatically doom it, but it triggers the second part of the test.

The second part asks whether the agreement was entered into freely and voluntarily, on independent advice, with both spouses having full knowledge of their rights. Two things matter most here. First, did both parties make a full disclosure of the amount, character, and value of the property involved, so that each knew what he or she was agreeing to give up? Second, was the agreement freely entered into, with independent counsel and full knowledge of the rights being surrendered? An agreement that is unfair on its face can still be enforced if the disadvantaged spouse genuinely understood it and signed it voluntarily. But an unfair agreement signed without disclosure, without independent advice, or under pressure is the kind that courts refuse to enforce.

The Four Pillars of an Enforceable Prenup

Evidence the court looks for under the Matson test.

Fairness

Reasonable terms

An agreement that leaves both spouses in a reasonable position can pass on substance alone.

Full disclosure

No signing blind

Each spouse laid out what they own and what it is worth, usually in an attached schedule.

Voluntariness

Time, not pressure

Signed weeks or months before the wedding, not on the courthouse steps.

Independent counsel

Separate attorneys

Each spouse had their own lawyer explain the rights being waived.

What Makes a Prenup Enforceable

Reading the Matson test in reverse tells you exactly what makes an agreement stand up. Four elements do most of the work.

Fairness comes first. An agreement that leaves both spouses in a reasonable position, rather than stripping one of them, has the easiest path to enforcement because it may satisfy the first part of the test on its own. Full financial disclosure comes next. Each spouse should have laid out what they own and what it is worth, usually in a schedule attached to the agreement, so neither can later claim to have signed blind. Voluntariness is third. The signature has to be a free choice, which is why timing matters so much and why last minute, pressure filled signings are so vulnerable to challenge. And independent legal counsel is fourth. When each spouse has their own attorney reviewing the agreement and explaining the rights being waived, it becomes very hard for either to argue later that they did not understand what they signed.

None of these is a mere formality. Each one is evidence the court will look for when deciding, under Matson, whether to enforce the agreement. The more of them you can show, the stronger your position when you present the prenup in the divorce.

Property and Support, Not Children

It helps to remember what a prenup can and cannot control when you go to enforce it. A valid prenup can direct how property is characterized and divided and can address spousal support, all subject to the Matson fairness review. It cannot dictate child custody or child support. Those are decided at the time of the divorce based on the child's best interests, under the parenting plan criteria in RCW 26.09.187 and the child support schedules in chapter 26.19 RCW, regardless of what any prenup says. So when you enforce a prenup, you are enforcing the property and spousal support terms. The parenting and support of any children ride on a separate track entirely.

Practical Steps If You Need to Enforce Yours

If you are heading into a divorce and want your prenup honored, the practical path runs through your family law attorney. You will bring the signed original, along with any financial disclosures and records of the independent legal advice each of you received, into the divorce proceeding. Your attorney presents the agreement and argues that it satisfies the Matson test, while being ready to answer any challenge that it was unfair, that disclosure was incomplete, or that the signature was not voluntary. If the court agrees the agreement is valid, it applies the terms and divides the property accordingly rather than falling back on the default community property statutes.

The strength of your position was largely set the day the agreement was drafted and signed. That is why the care put in at the front end, fairness, disclosure, timing, and independent counsel, pays off precisely at the moment you need to enforce it.

If you have a prenuptial agreement you may need to enforce, or you want one drafted so that it will actually hold up if that day comes, the Law Office of Chad Foster helps clients throughout Snohomish County. Reach out to talk through your agreement and your options.