Mo. Rev. Stat. § 145.481: Tax return required when — executor's duty.

A tax return with respect to the tax imposed by sections 145.011 to 145.995 shall be made:

(1) With respect to a resident, by every executor who is required to file a federal estate tax return;

(2) With respect to a nonresident, by every executor who is required to file a federal estate tax return if that part of the gross estate having a tax situs within the state of Missouri exceeds ten thousand dollars.