It is the duty of the executor to keep such complete and detailed records of the affairs of the estate for which he acts as will enable the district director to determine accurately the amount of the estate tax liability. All documents and vouchers used in preparing the estate tax return (§ 20.6018-1) shall be retained by the executor so as to be available for inspection whenever required.

In addition to filing an estate tax return (see § 20.6018-1) and, if applicable, a preliminary notice (see § 20.6036-1), the executor shall furnish such supplemental data as may be necessary to establish the correct estate tax. It is therefore the duty of the executor (1) to furnish, upon request, copies of any documents in his possession (or on file in any court having jurisdiction over the estate) relating to the estate, appraisal lists of any items included in the gross estate, copies of balance sheets or other financial statements obtainable by him relating to the value of stock, and any other information obtainable by him that may be found necessary in the determination of the tax, and (2) to render any written statement, containing a declaration that it is made under penalties of perjury, of facts within his knowledge which the district director may require for the purpose of determining whether a tax liability exists and, if so, the extent thereof. Failure to comply with such a request will render the executor liable to penalties (see section 7269), and proceedings may be instituted in the proper court of the United States to secure compliance therewith (see section 7604).

Persons having possession or control of any records or documents containing or supposed to contain any information concerning the estate, or having knowledge of or information about any fact or facts which have a material bearing upon the liability, or the extent of liability, of the estate for the estate tax, shall, upon request of the district director, make disclosure thereof. Failure on the part of any person to comply with such request will render him liable to penalties (section 7269), and compliance with the request may be enforced in the proper court of the United States (section 7604).

Upon notification from the Internal Revenue Service, a corporation (organized or created in the United States) or its transfer agent is required to furnish the following information pertaining to stocks or bonds registered in the name of a nonresident decedent (regardless of citizenship): (1) The name of the decedent as registered; (2) the date of the decedent's death; (3) the decedent's residence and his place of death; (4) the names and addresses of executors, attorneys, or other representatives of the estate, within and without the United States; and (5) a description of the securities, the number of shares or bonds and the par values thereof.