Mass. Gen. Laws ch. 65 § 13
Except as otherwise provided in this section and section fourteen, the tax imposed by this chapter shall be assessed upon the value of the property at the time of the death of the decedent. In case of a devise, descent, bequest or grant to take effect in possession or enjoyment after the expiration of one or more life estates or of a term of years, the tax shall be assessed on the value of the property or interest therein coming to the beneficiary at the time when he becomes entitled to the same in possession or enjoyment. The value of an annuity or a life interest in any such property, or any interest therein less than an absolute interest, shall be determined by the tables used by the United States Commissioner of Internal Revenue for the valuation of property interests under the federal estate tax law for persons dying on the valuation date in question and not the tables in effect on the date of death of the decedent who created the interest; but when an annuity or a life interest is terminated by the death of the annuitant or life tenant, and the tax upon such interest is not due and has not been paid in advance, the value of said interest for the purposes of taxation under this chapter shall be the amount of the annuity or income actually paid or payable to the annuitant or life tenant during the period for which he was entitled to the annuity or was in possession of the life estate.
Mass. Gen. Laws ch. 65, § 13