RCW 51.04.070

A minor shall be deemed sui juris for the purpose of this title, and no other person shall have any cause of action or right to compensation for an injury to such minor worker, except as expressly provided in this title, but in the event of any disability payments becoming due under this title to a minor worker, under the age of eighteen, such disability payments shall be paid to his or her parent, guardian or other person having legal custody of his or her person until he or she reaches the age of eighteen. Upon the submission of written authorization by any such parent, guardian, or other person, any such disability payments may be paid directly to such injured worker under the age of eighteen years. If it is necessary to appoint a legal guardian to receive such disability payments, there shall be paid from the accident fund or by the self-insurer, as the case may be, toward the expenses of such guardianship a sum not to exceed three hundred dollars.