Wash. Rev. Code § 59.18 § 59.18.720

(1)(a) Except as provided in subsection (2) of this section, a landlord must provide a tenant with notice of rent increases in a form that is substantially the same as the form provided in subsection (3) of this section.
(b) Notice under this section must also:
(i) Comply with the requirements in RCW 59.18.140 related to the number of days of prior written notice required for a rent increase; and
(ii) Be served in accordance with RCW 59.12.040 .
(2) The notice of rent increase requirement in this section does not apply if the rental agreement governs a subsidized tenancy where the amount of rent is based on, in whole or in part, a percentage of the income of the tenant or other circumstances specific to the subsidized household. However, for purposes of this section, a subsidized tenancy does not include tenancies where some or all of the rent paid to the landlord comes from a portable tenant-based voucher or similar portable assistance administered through a housing authority or other state or local agency, or tenancies in other types of affordable housing where maximum unit rents are limited by area median income levels and a tenant's base rent does not change as the tenant's income does.
(3) "TO TENANT(S): (tenant name(s))
AT ADDRESS: (tenant address)
RENT AND FEE INCREASE NOTICE TO TENANTS
This notice is required by Washington state law to inform you of your rights regarding rent and fee increases. Your rent or rental amount includes all recurring and periodic charges, sometimes referred to as rent and fees, identified in your rental agreement for the use and occupancy of your rental unit. Washington state limits how much your landlord can raise your rent and any other recurring or periodic charges for the use and occupancy of your rental unit.
(1) Your landlord can raise your rent and any other recurring or periodic charges identified in the rental agreement for use and occupancy of your rental unit once every 12 months by up to seven percent plus consumer price index, or 10 percent, whichever is less, as allowed by RCW 59.18.700 . Your landlord is not required to raise the rent or other recurring or periodic charges by any amount.
(2) Your landlord may be exempt from the limit on increases for rent and other recurring or periodic charges for the reasons described in RCW 59.18.710 . If your landlord claims an exemption, your landlord is required to include supporting facts with this notice.
(3) Your landlord must properly and fully complete the form below to notify you of any increases in rent and other recurring or periodic charges and any exemptions claimed.
Your landlord (name) intends to (check one of the following):
__ Raise your rent and/or other recurring or periodic charges: Your total increase for rent and other recurring or periodic charges effective (date) will be (percent), which totals an additional $(dollar amount) per month, for a new total amount of $(dollar amount) per month for rent and other recurring or periodic charges.
This increase for rent and/or other recurring or periodic charges is allowed by state law and is (check one of the following):
__ A lower increase than the maximum allowed by state law.
__ The maximum increase allowed by state law.
__ Authorized by an exemption under RCW 59.18.710 . If the increase is authorized by an exemption, your landlord must fill out the section of the form below.
EXEMPTIONS CLAIMED BY LANDLORD
I (landlord name) certify that I am allowed under Washington state law to raise your rent and other recurring or periodic charges by (percent), which is more than the maximum increase otherwise allowed by state law, because I am claiming the following exemption under RCW 59.18.710 (check one of the following):
__ The first certificate of occupancy for your dwelling unit was issued on (insert date), which is 12 or less years before the date of this increase notice for rent and other recurring or periodic charges. (The landlord must include facts or attach documents supporting the exemption.)
__ You live in a dwelling unit owned by a public housing authority, public development authority, or nonprofit organization where maximum rents are regulated by other laws or local, state, or federal affordable housing program requirements, or a qualified low-income housing development as defined in RCW 82.45.010 , where the property is owned by a public housing authority, public development authority, or nonprofit organization. (The landlord must include facts or attach documents supporting the exemption.)
__ You live in a qualified low-income housing development which was allocated federal low-income housing tax credits by the Washington state housing finance commission and there is an enforceable regulatory agreement under the low-income housing tax credit program. (The landlord must include facts or attach documents supporting the exemption.)
__ You live in a dwelling unit in which you share a bathroom or kitchen facility with the owner, and the owner maintains a principal residence at the residential real property. (The landlord must include facts or attach documents supporting the exemption.)
__ You live in a single-family owner-occupied residence in which the owner-occupant rents or leases no more than two units or bedrooms including, but not limited to, an attached or detached accessory dwelling unit. (The landlord must include facts or attach documents supporting the exemption.)
__ You live in a duplex, triplex, or fourplex in which the owner occupied one of the units as the owner's principal place of residence at the beginning of the tenancy, and the owner continues in occupancy. (The landlord must include facts or attach documents supporting the exemption.)"
(4) This section expires July 1, 2040.