From the Washington Department of Revenue website… 

There is a misconception that services are not subject to sales tax. This article clarifies that some services are indeed subject to retail sales tax. Following is a listing of services that are subject to sales tax when provided to consumers.

Construction services (WAC 458-20-170)

• Constructing and improving new or existing buildings and structures. Installing, repairing, cleaning, improving, constructing and decorating real or personal property for others
• Cleaning, fumigating, razing or moving structures, including painting and papering, cleaning and repairing furnaces and septic tanks, and snow removal
• Clearing land and moving earth 

Installation and repair services (WAC 458-20-173)

• Repairing, cleaning, installing, or decorating personal property for others
• Furnaces, septic tanks, vehicles, appliances, etc.

Landscape maintenance (WAC 458-20-226)

Providing tangible personal property with an operator (WAC 458-20-211)

Retail recreation services (WAC 458-20-183)

• Fishing Charters
• Day trips for sight-seeing
• Service charges on tickets to professional sporting events

Personal services

• Personal training services
• Tanning
• Tattooing
• Turkish and steam baths, including hot tubs
• Dating and escort services

Miscellaneous services

• Car wash (including self-service facilities) or detailing cars, trucks, campers, boats, etc. (WAC 458-20-173)
• Catering and personal chefs (WAC 458-20-119)
• Extended warranties and maintenance agreements (WAC 458-20-257)
• Vehicle Towing
• Automobile parking
• Telephone services (458-20-245)
• Digital automated services, remote access software, and digital goods (WAC 458-20-15503)
• Escrow services and abstract and title insurance (WAC 458-20-156)
• Credit bureau services, including credit worthiness and tenant screening services

RCW 82.04.050 defines “retail sales.”