Miss. Code Ann. § 27-9-61

The adoption of the estate tax laws in this chapter shall in nowise affect any right belonging to the state or suit, prosecution or proceeding pending at the time of its adoption, or any right which the state may have under the estate tax statutes of the state prior to or at the time of the taking effect of this chapter, whether suit or other proceedings have been actually begun or may hereafter be instituted. But as to the rights of the state and all parties interested as to estates of persons dying, or disposing of property, prior to the time of taking effect of this chapter, such right or liability shall survive and be enforced the same as if this chapter had not become effective.