26 USC 2044 - Certain property for which marital deduction was previously allowed

(a) General rule 
The value of the gross estate shall include the value of any property to which this section applies in which the decedent had a qualifying income interest for life.
(b) Property to which this section applies 
This section applies to any property if
(1) a deduction was allowed with respect to the transfer of such property to the decedent
(A) under section 2056 by reason of subsection (b)(7) thereof, or

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(B) under section 2523 by reason of subsection (f) thereof, and
(2) section 2519 (relating to dispositions of certain life estates) did not apply with respect to a disposition by the decedent of part or all of such property.
(c) Property treated as having passed from decedent 
For purposes of this chapter and chapter 13, property includible in the gross estate of the decedent under subsection (a) shall be treated as property passing from the decedent.