Wash. Rev. Code § 81.80.220
A household goods carrier shall not collect or receive a greater, less, or different remuneration for the transportation of property or for any service in connection therewith than the rates and charges that are either legally established and filed with the commission or are specified in the contract or contracts filed. A household goods carrier shall not refund or remit in any manner or by any device any portion of the rates and charges required to be collected by each tariff or contract or filing with the commission.
The commission may check the records of all carriers under this chapter and of those employing the services of the carrier to discover all discriminations, under or overcharges, and rebates, and may suspend or revoke permits for violations of this section.
The commission may refuse to accept any time schedule, tariff, or contract that, in the opinion of the commission, limits the service of a carrier to profitable trips only or to the carrying of high class commodities in competition with other carriers who give a complete service affording one carrier an unfair advantage over a competitor.
RCW 81.80.220