26 CFR § 20.2014-5 - Proof of credit.
(a) If the foreign death tax has not been determined and paid by the time the Federal estate tax return required by section 6018 is filed, credit may be claimed on the return in an estimated amount. However, before credit for the foreign death tax is finally allowed, satisfactory evidence, such as a statement by an authorized official of each country, possession or political subdivision thereof imposing the tax, must be submitted on Form 706CE certifying:
(1) The full amount of the tax (exclusive of any interest or penalties), as computed before allowance of any credit, remission, or relief;
(2) The amount of any credit, allowance, remission, or relief, and other pertinent information, including the nature of the allowance and a description of the property to which it pertains;
(3) The net foreign death tax payable after any such allowance;
(4) The date on which the death tax was paid, or if not all paid at one time, the date and amount of each partial payment; and
(5) A list of the property situated in the foreign country and subjected to its tax, showing a description and the value of the property.
(b) The following information must also be submitted whenever applicable:
(1) If any of the property subjected to the foreign death tax was situated outside of the country imposing the tax, the description of each item of such property and its value.
(2) If more than one inheritance or succession is involved with respect to which credit is claimed, or if the foreign country, possession or political subdivision thereof imposes more than one kind of death tax, or if both the foreign country and a possession or political subdivision thereof each imposes a death tax, a separate computation with respect to each inheritance or succession tax.
(c) In addition to the information required under paragraphs (a) and (b) of this section, the district director may require the submission of any further proof deemed necessary to establish the right to the credit.