Mo. Rev. Stat. § 429.614: Broker to mail copy of notice of lien to owner by certified mail.

Any real estate broker who attaches a lien on commercial property pursuant to the provisions of sections 429.600 to 429.627 shall mail a copy of the notice of the lien to the owner of the commercial real estate by certified mail. The real estate broker's lien is void if the broker does not record the lien as provided in sections 429.600 to 429.627.