Mo. Rev. Stat. § 701.053: Registered on-site disposal system contractor, form, qualifications — registration issued by county to be deemed state registration.

1. A person may not represent himself as a registered on-site sewage disposal system contractor in this state unless the person is registered by a county or the department. A county or the department shall issue registration to a contractor if the contractor completes an application form that is in compliance with sections 701.025 to 701.059 and the rules and regulations adopted thereunder. A registration issued by a county in compliance with sections 701.053 to 701.055 shall be considered a state registration and valid in all political subdivisions of the state.

2. To qualify for registration, a contractor must successfully complete the educational training program provided by the department, or a county that offers on-site sewage disposal system contractor training that has been certified by the department and has an ordinance or regulation that mandates contractor training.