Miss. Code § 27-9-23
Within nine (9) months, or any extensions thereof, after the death of the decedent, the executor shall make a return in all cases where the gross estate at the time of death of the decedent exceeds the amount of the specific exemption provided in Section 27-9-11 and in the estate of every nonresident when any part of his gross estate is situated within the State of Mississippi. If the executor is unable to make a complete return as to any part of the gross estate of the decedent, he shall include in his return a description of such property, and the name of every person holding a legal or beneficial interest therein, and upon notice from the commissioner such persons shall in like manner make a return as to such part of the gross estate. Provided, however, the tax due upon farms and closely held businesses shall be due and payable at the time the federal estate tax return is due and payable.
Miss. Code § 27-9-23