Washington Postnuptial Agreement

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Updated January 23, 2023

A Washington postnuptial agreement is a contract married couples use to establish property rights and obligations in the event their marriage ends in divorce or death.

Postnuptial agreements may be beneficial in the event of a divorce because they enable couples to exempt certain assets from Washington’s traditional community property rules. In this, they resemble prenuptial agreements, commonly called “prenups.” But unlike prenups, which are signed before marriage, postnuptial agreements are signed once a couple has already been married.

Signing Requirements – Agreements may be oral or written, but verbal agreements are more difficult to prove. In re G.W.-F. (2012). If the agreement is effective on the death of the other spouse, then it must be in writing, signed by both spouses, witnessed, and notarized. Wash. Rev. Code Ann. § 26.16.120.


Community Property: Partners in a committed intimate relationship, like spouses, may change the status of their community-like property to separate property by entering into mutual agreements. In re G.W.-F. (2012).

Application at Death: Spouses or domestic partners may jointly agree to the status or disposition of the whole or any portion of the community property, then owned by them or afterward to be acquired, to take effect upon either death. Wash. Rev. Code Ann. § 26.16.120.

Oral vs. Written Agreement: Courts will overturn an oral property agreement if the parties do not consistently adhere to it during their relationship. In re G.W.-F. (2012).

Validity: There is a two-pronged test for evaluating the validity of a postnuptial agreement. In re G.W.-F. (2012).

First, the court must decide whether the agreement provides a fair and reasonable provision for the party not seeking enforcement of the agreement. If the agreement is fair and reasonable, and the challenging party has not shown fraud or overreaching, the analysis ends, and the agreement may be validated. Matter of Marriage of Matson (1986).

The second prong requires the court to examine the procedural fairness of the contract by asking two questions:

  1. Whether the parties fully disclose the amount, character, and value of the property involved, and;
  2. Whether the agreement was entered into by both spouses, fully and voluntarily on independent advice and with full knowledge of their rights.

In re G.W.-F. (2012).