Wash. Admin. Code § 480-30-022
A passenger transportation company may contract with a person or company to perform tasks that are subject to the rules under this chapter. If the passenger transportation company's contractor or any of its subcontractors engages in conduct that violates any federal, state, or local law or regulation, or any commission order, while performing tasks under the contract, the passenger transportation company is subject to commission enforcement actions as if the passenger transportation company itself engaged in that conduct. The passenger transportation company is responsible for maintaining measures designed to prevent and detect a violation of statutes or rules within the commission's authority to enforce by a contractor or any of its subcontractors. The passenger transportation company must make available records regarding its use of the contractor on request by the commission that fully enable the commission to audit, investigate, and determine the company's compliance with applicable law while using the contractor.
Wash. Admin. Code § 480-30-022