26 CFR § 20.2002-1 - Liability for payment of tax.
The Federal estate tax imposed both with respect to the estates of citizens or residents and with respect to estates of nonresidents not citizens is payable by the executor or administrator of the decedent's estate. This duty applies to the entire tax, regardless of the fact that the gross estate consists in part of property which does not come within the possession of the executor or administrator. If there is no executor or administrator appointed, qualified and acting in the United States, any person in actual or constructive possession of any property of the decedent is required to pay the entire tax to the extent of the value of the property in his possession. See section 2203, defining the term “executor”. The personal liability of the executor or such other person is described in section 3467 of the Revised Statutes (31 U.S.C. 192) as follows:
Every executor, administrator, or assignee, or other person, who pays, in whole or in part, any debt due by the person or estate for whom or for which he acts before he satisfies and pays the debts due to the United States from such person or estate, shall become answerable in his own person and estate to the extent of such payments for the debts so due to the United States, or for so much thereof as may remain due and unpaid.