Wash. Rev. Code § 30A.22.170
Any funds on deposit in an account may be paid by a financial institution to or upon the order of any agent of any depositor. The contract of deposit or other document creating such agency may provide, in accordance with chapter 11.125 RCW, that any such agent's powers to receive payments and make withdrawals from an account continues in spite of, or arises by virtue of, the incompetency of a depositor, in which event the agent's powers to make payments and withdrawals from an account on behalf of a depositor is not affected by the incompetency of a depositor. Except as provided in this section, the authority of an agent to receive payments or make withdrawals from an account terminates with the death or incompetency of the agent's principal: PROVIDED, That a financial institution is not liable for any payment or withdrawal made to or by an agent for a deceased or incompetent depositor unless the financial institution making the payment or permitting the withdrawal had actual knowledge of the incompetency or death at the time payment was made.
RCW 30A.22.170
Short title-Application-Uniformity-Federal law application-Federal electronic signatures in global and national commerce act-Application-Dates-Effective date- 2016 c 209 : See RCW 11.125.010 and 11.125.900 through 11.125.903.