Washington Revised Code Title 19. Business Regulations--Miscellaneous § 19.80.040. Failure to file

No person or persons carrying on, conducting, or transacting business under any trade name shall be entitled to maintain any suit in any of the courts of this state until such person or persons have properly completed the registration as provided for in RCW 19.80.010. Failure to complete this registration shall not impair the validity of any contract or act of such person or persons and shall not prevent such person or persons from defending any suit in any court of this state.