Wash. Rev. Code § 59.18 § 59.18.125

(1) Local municipalities may require that landlords provide a certificate of inspection as a business license condition. A local municipality does not need to have a business license or registration program in order to require that landlords provide a certificate of inspection. A certificate of inspection does not preclude or limit inspections conducted pursuant to the tenant remedy as provided for in RCW 59.18.115 , at the request or consent of the tenant, or pursuant to a warrant.
(2) A qualified inspector who is conducting an inspection under this section may only investigate a rental property as needed to provide a certificate of inspection.
(3) A local municipality may only require a certificate of inspection on a rental property once every three years.
(4)(a) A rental property that has received a certificate of occupancy within the last four years and has had no code violations reported on the property during that period is exempt from inspection under this section.
(b) A rental property inspected by a government agency or other qualified inspector within the previous twenty-four months may provide proof of that inspection which the local municipality may accept in lieu of a certificate of inspection. If any additional inspections of the rental property are conducted, a copy of the findings of these inspections may also be required by the local municipality.
(5) A rental property owner may choose to inspect one hundred percent of the units on the rental property and provide only the certificate of inspection for all units to the local municipality. However, if a rental property owner chooses to inspect only a sampling of the units, the owner must send written notice of the inspection to all units at the property. The notice must advise tenants that some of the units at the property will be inspected and that the tenants whose units need repairs or maintenance should send written notification to the landlord as provided in RCW 59.18.070 . The notice must also advise tenants that if the landlord fails to adequately respond to the request for repairs or maintenance, the tenants may contact local municipality officials. A copy of the notice must be provided to the inspector upon request on the day of inspection.
(6)(a) If a rental property has twenty or fewer dwelling units, no more than four dwelling units at the rental property may be selected by the local municipality to provide a certificate of inspection as long as the initial inspection reveals that no conditions exist that endanger or impair the health or safety of a tenant.
(b) If a rental property has twenty-one or more units, no more than twenty percent of the units, rounded up to the next whole number, on the rental property, and up to a maximum of fifty units at any one property, may be selected by the local municipality to provide a certificate of inspection as long as the initial inspection reveals that no conditions exist that endanger or impair the health or safety of a tenant.
(c) If a rental property is asked to provide a certificate of inspection for a sample of units on the property and a selected unit fails the initial inspection, the local municipality may require up to one hundred percent of the units on the rental property to provide a certificate of inspection.
(d) If a rental property has had conditions that endanger or impair the health or safety of a tenant reported since the last required inspection, the local municipality may require one hundred percent of the units on the rental property to provide a certificate of inspection.
(e) If a rental property owner chooses to hire a qualified inspector other than a municipal housing code enforcement officer, and a selected unit of the rental property fails the initial inspection, both the results of the initial inspection and any certificate of inspection must be provided to the local municipality.
(7)(a) The landlord shall provide written notification of his or her intent to enter an individual unit for the purposes of providing a local municipality with a certificate of inspection in accordance with RCW 59.18.150 (6). The written notice must indicate the date and approximate time of the inspection and the company or person performing the inspection, and that the tenant has the right to see the inspector's identification before the inspector enters the individual unit. A copy of this notice must be provided to the inspector upon request on the day of inspection.
(b) A tenant who continues to deny access to his or her unit is subject to RCW 59.18.150 (8).
(8) If a rental property owner does not agree with the findings of an inspection performed by a local municipality under this section, the local municipality shall offer an appeals process.
(9) A penalty for noncompliance under this section may be assessed by a local municipality. A local municipality may also notify the landlord that until a certificate of inspection is provided, it is unlawful to rent or to allow a tenant to continue to occupy the dwelling unit.
(10) Any person who knowingly submits or assists in the submission of a falsified certificate of inspection, or knowingly submits falsified information upon which a certificate of inspection is issued, is, in addition to the penalties provided for in subsection (9) of this section, guilty of a gross misdemeanor and must be punished by a fine of not more than five thousand dollars.
(11) As of June 10, 2010, a local municipality may not enact an ordinance requiring a certificate of inspection unless the ordinance complies with this section. This prohibition does not preclude any amendments made to ordinances adopted before June 10, 2010.