RCW 26.16.140: Earnings and accumulations of spouses or domestic partners living apart, minor children.

When spouses or domestic partners are living separate and apart, their respective earnings and accumulations shall be the separate property of each. The earnings and accumulations of minor children shall be the separate property of the spouse or domestic partner who has their custody or, if no custody award has been made, then the separate property of the spouse or domestic partner with whom said children are living.