King County, WA Rental Property Rules: Rental Registration (2026)

King County itself does not require rental property registration or licensing for long-term residential rentals in unincorporated areas. Landlords are subject to Washington state requirements: a Washington State Business License (through the Department of Revenue) is required for most residential landlords under RCW 59.18.060 and state tax law, with limited small-landlord exceptions. Specific notices must include the landlords name and address under RCW 59.18.060, lead-based paint disclosures for pre-1978 rentals under federal law, and a summary of the Landlord-Tenant Act under RCW 59.18.257 for new tenants. Short-term rentals (Airbnb-type, under 30 days) are a separate category and may require additional registration, sales tax collection, and compliance with state lodging tax; some incorporated cities in King County regulate STRs more tightly. Several cities within King County run rental registration programs: Seattles Rental Registration and Inspection Ordinance (RRIO) requires registration of all rental units and periodic inspection; Burien, Kent, Auburn, and several others have their own programs. If you rent in an incorporated city, check that city ordinance. In unincorporated King County, code enforcement can still inspect rentals for habitability, safety, and zoning compliance upon complaint, and landlords must comply with KCC Title 21A occupancy and development standards.