What Is the Difference Between Prenups and Postnups?

The short answer is timing: a prenuptial agreement is signed before the wedding, and a postnuptial agreement is signed after the couple is already married. Beyond that single difference, the two documents do much the same work and must clear the same legal bar to be enforced, which is why couples in Snohomish County often ask how to choose between them. This topic is part of Washington prenuptial and postnuptial agreements.

Same Purpose, Different Moment

A prenup and a postnup are both marital property agreements. Each is a written contract in which spouses, or spouses-to-be, decide for themselves how their property and debts will be treated, rather than leaving those questions entirely to Washington's default rules. Washington is a community property state, which means the law sorts what a couple owns and owes into separate property and community property. Separate property, generally what a spouse brings into the marriage or receives by gift or inheritance, is defined in RCW 26.16.010. Community property, generally what is acquired during the marriage, is defined in RCW 26.16.030. A prenup or postnup lets the couple adjust how those categories apply to their own finances. Related guides cover Talking to Your Partner About a Prenup and What Happens If We Don't Have a Prenup?.

The only structural difference is when the agreement is signed. A prenup is executed before the marriage, and it takes effect when the couple weds. A postnup is executed after the couple is already married, when circumstances have shifted. Maybe one spouse launched a business, received an inheritance, or the couple simply decided they wanted the clarity a formal agreement provides. Life does not always give people the foresight to sort out these questions before the wedding. A postnup is the tool for couples who are already married and want to set clear terms now.

The Same Fairness Test Governs Both

Here is what many people do not realize: prenups and postnups are judged by the very same standard in Washington. There is no statute that lays out when one of these agreements is valid. The rules come from case law, and the leading case is In re Marriage of Matson, 107 Wn.2d 479 (1986). Matson established a two-part fairness test that Washington courts apply to marital property agreements regardless of whether they were signed before or after the wedding.

The first part asks whether the agreement is substantively fair, meaning whether it makes a fair and reasonable provision for the spouse who is not seeking to enforce it. If the agreement is fair on its face, it can stand on that basis alone. If it is not, the court turns to the second part, procedural fairness, which asks two questions. Did the spouses make a full disclosure of the amount, character, and value of their property? And did each spouse enter the agreement voluntarily, with independent advice and full knowledge of the rights being given up? The Washington Supreme Court reaffirmed this framework in In re Marriage of Bernard, 165 Wn.2d 895 (2009), and it applies to postnuptial agreements just as it does to prenuptial ones. In fact, courts have analyzed postnuptial amendments under this same two-prong approach.

So whether a couple signs before or after the wedding, the practical advice is identical. Both spouses need to disclose their finances honestly, both need enough time to review the agreement without pressure, and both should have the opportunity to consult their own attorney. An agreement that is lopsided and rushed is vulnerable no matter when it was signed.

A Word About Community Property Agreements

There is a third document that people often confuse with a prenup or postnup, and it is worth separating out clearly. A community property agreement is a distinct estate-planning tool, not a divorce agreement. Washington law expressly allows spouses to enter into an agreement about the status of their community property that takes effect upon the death of either spouse. That authority comes from RCW 26.16.120, and the key phrase in the statute is that the agreement is designed "to take effect upon the death of either."

That death-effective trigger is what sets a community property agreement apart. It is an estate-planning device meant to move property smoothly to a surviving spouse and, in many cases, avoid probate. It is not designed to divide property in a divorce, and it should not be confused with a prenup or postnup, which are meant to govern how property is characterized if the marriage ends by dissolution. A couple who wants to plan for divorce needs a prenuptial or postnuptial agreement tested under the Matson standard. A couple who wants to plan for what happens at death is looking at a community property agreement under RCW 26.16.120. The documents serve different purposes, and using the wrong one for the wrong goal can leave a couple unprotected exactly where they thought they were covered.

What Neither Document Can Do

Whether prenup or postnup, a marital property agreement cannot decide child custody or child support in advance. Those questions turn on a child's best interests at the time they arise, and the court retains authority over them. A couple can settle a great deal about their property and debts, but they cannot contract away the court's role in protecting children.

Choosing the Right Agreement for Your Situation

For most couples, the choice between a prenup and a postnup comes down to where they are in life. If the wedding is still ahead, a prenup lets you start the marriage with clear terms. If you are already married and circumstances have changed, a postnup can bring that same clarity now. Either way, the agreement is only as strong as the fairness behind it.

If you are weighing a prenuptial or postnuptial agreement in Snohomish County, or you are not sure which fits your circumstances, the Law Office of Chad Foster can help you understand the difference and choose the right path. Reach out to talk it over.