Wash. Rev. Code § 20.01.080
Any person applying for a commission merchant's license shall include in his or her application a schedule of commissions, together with an itemized list of all charges for services to be rendered to a consignor and shall post a copy of such charges on his or her premises in a conspicuous place where it is clearly visible and available to consignors. In addition to the posting of the itemized list of charges, such list shall be distributed to each consignor along with each contract entered into between the consignor and the commission merchant. Such commissions and charges shall not be changed or varied for the license period except by written contract between the consignor or his or her agent and the licensee or thirty days after written notice to the director, and proper posting of such changes, as prescribed by the director, on the licensee's premises. Charges for services rendered and not listed on the schedule of commissions and charges filed with the director, or for increases in charges listed and filed which are directly caused by increases in labor rates or in cost of materials which occur after the signing of the contract by the grower, shall be rendered only on an actual cost to the licensee basis.
RCW 20.01.080