Mississippi Code Title 91. Trusts and Estates § 91-25-27

(a) This chapter does not apply to the estate of a decedent who dies on or within one (1) year after July 1, 2020, nor with respect to a decedent who dies more than one (1) year after July 1, 2020, if the decedent continuously lacked testamentary capacity from the expiration of the one-year period until the date of death.

(b) With respect to a decedent who dies on or after July 1, 2020, to whom this chapter does not apply, estate taxes must be apportioned under the law in effect on the day before July 1, 2020.

(c) Notwithstanding the provisions of subsections (a) and (b), this chapter applies with respect to a decedent to whom the provisions would not otherwise apply if the decedent expressly and unambiguously directs that the provisions shall apply to such decedent.