AGO 1961 NO. 67 >
(1) RCW 59.18.270 does not require a landlord to maintain separate account for each tenant's security deposit; accordingly, the landlord may maintain a single account for the security deposits of all his tenants. (2) If interest is earned through the investment of a tenant's security deposit, that interest belongs to the tenant. (3) Interest earned on a tenant's security deposit may be retained by the landlord as a part of his rental charges for the premises involved if express provision to that effect is included in the rental agreement.