Mass. Gen. Laws ch. 65A § 1
A tax is hereby imposed upon the transfer of the estate of every person dying after February twenty-sixth, nineteen hundred and twenty-six, who at the time of death was a resident of this commonwealth, the amount of which shall be the amount by which eighty per cent of the estate tax payable to the United States under the provisions of the federal revenue act of nineteen hundred and twenty-six shall exceed the aggregate amount of all estate, inheritance, legacy and succession taxes actually paid to the several states of the United States in respect to any property owned by such decedent or subject to such taxes as a part of or in connection with his estate.
A tax is hereby imposed upon the transfer of the estate of every person who at the time of death was a resident of this commonwealth and whose estate is subject to an estate tax imposed under any act of congress subsequent to the federal revenue act of nineteen hundred and twenty-six, the amount of which shall be the amount by which the federal credit under such federal revenue act shall exceed the aggregate amount of all estate, inheritance, legacy and succession taxes actually paid to the several states of the United States in respect to any property owned by such decedent or subject to such taxes as a part of or in connection with his estate.
A tax is hereby imposed upon the transfer of real property or tangible personal property in the commonwealth of every person who at the time of death was a resident of the United States but not a resident of the commonwealth, and upon the transfer of all property, both real and personal, within the commonwealth of every person who at the time of death was not a resident of the United States, the amount of which shall be a sum equal to such proportion of the amount by which the credit allowable under the applicable federal revenue act for estate, inheritance, legacy and succession taxes actually paid to the several states exceeds the amount actually so paid for such taxes, exclusive of estate taxes based upon the difference between such credit and other estate taxes and inheritance, legacy and succession taxes, as the value of the property in the commonwealth bears to the value of the entire estate, subject to estate tax under the applicable federal revenue act.
Mass. Gen. Laws ch. 65A, § 1