adjusted gross estate
(6) Adjusted gross estate For purposes of this section, the term, “adjusted gross estate” means the value of the gross estate reduced by the sum of the amounts allowable as a deduction under section 2053 or 2054. Such sum shall be determined on the basis of the facts and circumstances in existence on the date (including extensions) for filing the return of tax imposed by section 2001 (or, if earlier, the date on which such return is filed).