RCW 11.140.050: Transfer to custodial trustee by fiduciary or obligor—Facility of payment.

(1) Unless otherwise directed by an instrument designating a custodial trustee pursuant to RCW 11.140.030, a person, including a fiduciary other than a custodial trustee, who holds property of or owes a debt to an incapacitated individual not having a conservator may make a transfer to an adult member of the beneficiary's family or to a trust company as custodial trustee for the use and benefit of the incapacitated individual. If the value of the property or the debt exceeds $20,000, the transfer is not effective unless authorized by the court.

(2) A written acknowledgment of delivery, signed by a custodial trustee, is a sufficient receipt and discharge for property transferred to the custodial trustee pursuant to this section.