Mo. Rev. Stat. § 382.100
Every insurer which is authorized to do business in this state and which is a member of an insurance holding company system, except a foreign insurer subject to disclosure requirements and standards adopted by statute or regulation in the jurisdiction of its domicile which are substantially similar to those contained in sections 382.010 to 382.300, shall register with the director. Every insurer which is subject to registration under sections 382.010 to 382.300 shall register within sixty days after September 28, 1971, or fifteen days after it becomes subject to registration, whichever is later, and annually thereafter by March first of each year for the previous calendar year, unless the director for good cause shown extends the time for registration, and then within such extended time. The director may require any authorized insurer which is a member of a holding company system which is not subject to registration under this section to furnish a copy of the registration statement, the summary specified in subsection 2 of section 382.110, or other information filed by it with the insurance regulatory authority of its state of domicile.
§ 382.100, RSMo