Wash. Rev. Code § 59.20 § 59.20.170

(1) For leases or rental agreements entered into on or after May 7, 2025, if a landlord charges a tenant any move-in fees or security deposits, the move-in fees and security deposits combined may not exceed one month's rent, unless the tenant brings any pets into the tenancy, in which case the move-in fees and security deposits combined may not exceed two months' rent. This subsection (1) does not apply to leases or rental agreements entered into before May 7, 2025, even if such leases or rental agreements are renewed on or after May 7, 2025.
(2) All moneys paid to the landlord by the tenant as a deposit as security for performance of the tenant's obligations in a rental agreement shall promptly be deposited by the landlord in a trust account, maintained by the landlord for the purpose of holding such security deposits for tenants of the landlord, in a financial institution as defined by RCW 30A.22.041 or licensed escrow agent located in Washington. Unless otherwise agreed in writing, the landlord shall be entitled to receipt of interest paid on such trust account deposits. The landlord shall provide the tenant with a written receipt for the deposit and shall provide written notice of the name and address and location of the depository and any subsequent change thereof. If during a tenancy the status of landlord is transferred to another, any sums in the deposit trust account affected by such transfer shall simultaneously be transferred to an equivalent trust account of the successor landlord, and the successor landlord shall promptly notify the tenant of the transfer and of the name, address and location of the new depository. The tenant's claim to any moneys paid under this section shall be prior to that of any creditor of the landlord, including a trustee in bankruptcy or receiver, even if such moneys are commingled.