Mo. Rev. Stat. § 374.245: Director or director of revenue may make supplemental assessment for certain premium taxes, when.

The director of the department of commerce and insurance or the director of revenue may, within three years after a return is filed or at any time if no return is filed, make a supplemental assessment or certification whenever it is found that any assessment or certification of premium taxes covered by this section is imperfect or incomplete in any material aspect. The provisions of this section shall apply to taxes assessed under sections 148.310 to 148.461, and sections 287.690, and 375.916.