Wash. Rev. Code § 59.18 § 59.18.610

(1)(a) Except as provided in (b) of this subsection, upon receipt of a tenant's written request, a landlord must permit the tenant to pay any deposits, nonrefundable fees, and last month's rent in installments.
(b) A landlord is not required to permit a tenant to pay in installments if the total amount of the deposits and nonrefundable fees do not exceed twenty-five percent of the first full month's rent and payment of the last month's rent is not required at the inception of the tenancy.
(2) In all cases where premises are rented for a specified time that is three months or longer, the tenant may elect to pay any deposits, nonrefundable fees, and last month's rent in three consecutive and equal monthly installments, beginning at the inception of the tenancy. In all other cases, the tenant may elect to pay any deposits, nonrefundable fees, and last month's rent in two consecutive and equal monthly installments, beginning at the inception of the tenancy.
(3) A landlord may not impose any fee, charge any interest, or otherwise impose a cost on a tenant because a tenant elects to pay in installments. Installment payments are due at the same time as rent is due. All installment schedules must be in writing and signed by the landlord and the tenant.
(4)(a) A fee or deposit to hold a dwelling unit or secure that the prospective tenant will move into a dwelling unit, as authorized under RCW 59.18.253 , shall not be considered a deposit or nonrefundable fee for purposes of this section.
(b) A landlord may not request a fee or deposit to hold a dwelling unit or secure that the prospective tenant will move into a dwelling unit in excess of twenty-five percent of the first month's rent.
(5) Beginning January 1, 2021, any landlord who refuses to permit a tenant to pay any deposits, nonrefundable fees, and last month's rent in installments upon the tenant's written request as described in subsection (1) of this section is subject to a statutory penalty of one month's rent and reasonable attorneys' fees payable to the tenant.
(6)(a) In any application seeking relief pursuant [to] RCW 59.18.283 (3), the court shall issue a finding as to whether the tenant is low-income, limited resourced, or experiencing hardship to determine if the landlord would be eligible for reimbursement through the landlord mitigation program account established within *RCW 43.31.605 (1)(c). In making this finding, the court may include an inquiry regarding the tenant's income relative to area median income, household composition, any extenuating circumstances, or other factors, and may rely on written declarations or oral testimony by the parties at the hearing.
(b) After a finding that the tenant is low-income, limited resourced, or experiencing hardship, the court may issue an order: (i) Finding that the landlord is eligible to receive on behalf of the tenant and may apply for reimbursement from the landlord mitigation program; and (ii) directing the clerk to remit, without further order of the court, any future payments made by the tenant in order to reimburse the department of commerce pursuant to *RCW 43.31.605 (1)(c)(iii). Nothing in this subsection shall be deemed to obligate the department of commerce to provide assistance in claim reimbursement through the landlord mitigation program if there are not sufficient funds.
(c) Upon payment by the department of commerce to the landlord for the remaining or total amount of the judgment, as applicable, the judgment is satisfied and the landlord shall file a satisfaction of judgment with the court.