Wash. Rev. Code § 26.16.120
Nothing contained in any of the provisions of *this chapter or in any law of this state, shall prevent both spouses or both domestic partners from jointly entering into any agreement concerning the status or disposition of the whole or any portion of the community property, then owned by them or afterwards to be acquired, to take effect upon the death of either. But such agreement may be made at any time by both spouses or both domestic partners by the execution of an instrument in writing under their hands and seals, and to be witnessed, acknowledged and certified in the same manner as deeds to real estate are required to be, under the laws of the state, and the same may at any time thereafter be altered or amended in the same manner. Such agreement shall not derogate from the right of creditors; nor be construed to curtail the powers of the superior court to set aside or cancel such agreement for fraud or under some other recognized head of equity jurisdiction, at the suit of either party; nor prevent the application of laws governing the community property and inheritance rights of slayers or abusers under chapter 11.84 RCW.
RCW 26.16.120
*Reviser's note: "this chapter", which is Code 1881, chapter CLXXXIII, is codified as RCW 26.16.010 through 26.16.040, 26.16.060, 26.16.120, 26.16.140 through 26.16.160, and 26.16.180 through 26.16.210.
Part headings not law-Severability-2008 c 6: See RCW 26.60.900 and 26.60.901.
Application-Conflict with federal requirements-1998 c 292: See notes following RCW 41.04.273.
Effective dates-1998 c 292: See RCW 11.11.903.
Acknowledgments: Chapter 64.08 RCW.
Descent and distribution of community property: RCW 11.04.015.
Private seals abolished: RCW 64.04.090.