For purposes of the tax imposed by section 2001, the value of the taxable estate shall, except as limited by subsection (b), be determined by deducting from the value of the gross estate an amount equal to the value of any interest in property which passes or has passed from the decedent to his surviving spouse, but only to the extent that such interest is included in determining the value of the gross estate.

Where, on the lapse of time, on the occurrence of an event or contingency, or on the failure of an event or contingency to occur, an interest passing to the surviving spouse will terminate or fail, no deduction shall be allowed under this section with respect to such interest—

Where, on the lapse of time, on the occurrence of an event or contingency, or on the failure of an event or contingency to occur, an interest passing to the surviving spouse will terminate or fail, no deduction shall be allowed under this section with respect to such interest—

(A) if an interest in such property passes or has passed (for less than an adequate and full consideration in money or money’s worth) from the decedent to any person other than such surviving spouse (or the estate of such spouse); and

(B) if by reason of such passing such person (or his heirs or assigns) may possess or enjoy any part of such property after such termination or failure of the interest so passing to the surviving spouse;

(C) if such interest is to be acquired for the surviving spouse, pursuant to directions of the decedent, by his executor or by the trustee of a trust.

(2) Interest in unidentified assets Where the assets (included in the decedent’s gross estate) out of which, or the proceeds of which, an interest passing to the surviving spouse may be satisfied include a particular asset or assets with respect to which no deduction would be allowed if such asset or assets passed from the decedent to such spouse, then the value of such interest passing to such spouse shall, for purposes of subsection (a), be reduced by the aggregate value of such particular assets.

For purposes of this subsection, an interest passing to the surviving spouse shall not be considered as an interest which will terminate or fail on the death of such spouse if—

(A) such death will cause a termination or failure of such interest only if it occurs within a period not exceeding 6 months after the decedent’s death, or only if it occurs as a result of a common disaster resulting in the death of the decedent and the surviving spouse, or only if it occurs in the case of either such event; and

(B) such termination or failure does not in fact occur.

In determining for purposes of subsection (a) the value of any interest in property passing to the surviving spouse for which a deduction is allowed by this section—

(A) there shall be taken into account the effect which the tax imposed by section 2001, or any estate, succession, legacy, or inheritance tax, has on the net value to the surviving spouse of such interest; and

(B) where such interest or property is encumbered in any manner, or where the surviving spouse incurs any obligation imposed by the decedent with respect to the passing of such interest, such encumbrance or obligation shall be taken into account in the same manner as if the amount of a gift to such spouse of such interest were being determined.

In the case of an interest in property passing from the decedent, if his surviving spouse is entitled for life to all the income from the entire interest, or all the income from a specific portion thereof, payable annually or at more frequent intervals, with power in the surviving spouse to appoint the entire interest, or such specific portion (exercisable in favor of such surviving spouse, or of the estate of such surviving spouse, or in favor of either, whether or not in each case the power is exercisable in favor of others), and with no power in any other person to appoint any part of the interest, or such specific portion, to any person other than the surviving spouse—

(A) the interest or such portion thereof so passing shall, for purposes of subsection (a), be considered as passing to the surviving spouse, and

(B) no part of the interest so passing shall, for purposes of paragraph (1)(A), be considered as passing to any person other than the surviving spouse.

In the case of an interest in property passing from the decedent consisting of proceeds under a life insurance, endowment, or annuity contract, if under the terms of the contract such proceeds are payable in installments or are held by the insurer subject to an agreement to pay interest thereon (whether the proceeds, on the termination of any interest payments, are payable in a lump sum or in annual or more frequent installments), and such installment or interest payments are payable annually or at more frequent intervals, commencing not later than 13 months after the decedent’s death, and all amounts, or a specific portion of all such amounts, payable during the life of the surviving spouse are payable only to such spouse, and such spouse has the power to appoint all amounts, or such specific portion, payable under such contract (exercisable in favor of such surviving spouse, or of the estate of such surviving spouse, or in favor of either, whether or not in each case the power is exercisable in favor of others), with no power in any other person to appoint such amounts to any person other than the surviving spouse—

(A) such amounts shall, for purposes of subsection (a), be considered as passing to the surviving spouse, and

(B) no part of such amounts shall, for purposes of paragraph (1)(A), be considered as passing to any person other than the surviving spouse.

In the case of qualified terminable interest property—

(A) In generalIn the case of qualified terminable interest property— (i) for purposes of subsection (a), such property shall be treated as passing to the surviving spouse, and (ii) for purposes of paragraph (1)(A), no part of such property shall be treated as passing to any person other than the surviving spouse.

(B) Qualified terminable interest property definedFor purposes of this paragraph— (i) In generalThe term “qualified terminable interest property” means property— (I) which passes from the decedent, (II) in which the surviving spouse has a qualifying income interest for life, and (III) to which an election under this paragraph applies. (ii) Qualifying income interest for lifeThe surviving spouse has a qualifying income interest for life if— (I) the surviving spouse is entitled to all the income from the property, payable annually or at more frequent intervals, or has a usufruct interest for life in the property, and (II) no person has a power to appoint any part of the property to any person other than the surviving spouse.  Subclause (II) shall not apply to a power exercisable only at or after the death of the surviving spouse. To the extent provided in regulations, an annuity shall be treated in a manner similar to an income interest in property (regardless of whether the property from which the annuity is payable can be separately identified). (iii) Property includes interest therein The term “property” includes an interest in property. (iv) Specific portion treated as separate prop­erty A specific portion of property shall be treated as separate property. (v) Election An election under this paragraph with respect to any property shall be made by the executor on the return of tax imposed by section 2001. Such an election, once made, shall be irrevocable.

(C) Treatment of survivor annuitiesIn the case of an annuity included in the gross estate of the decedent under section 2039 (or, in the case of an interest in an annuity arising under the community property laws of a State, included in the gross estate of the decedent under section 2033) where only the surviving spouse has the right to receive payments before the death of such surviving spouse— (i) the interest of such surviving spouse shall be treated as a qualifying income interest for life, and (ii) the executor shall be treated as having made an election under this subsection with respect to such annuity unless the executor otherwise elects on the return of tax imposed by section 2001. An election under clause (ii), once made, shall be irrevocable.

For purposes of subparagraph (A)—

(A) In general If the surviving spouse of the decedent is the only beneficiary of a qualified charitable remainder trust who is not a charitable beneficiary nor an ESOP beneficiary, paragraph (1) shall not apply to any interest in such trust which passes or has passed from the decedent to such surviving spouse.

(B) DefinitionsFor purposes of subparagraph (A)— (i) Charitable beneficiary The term “charitable beneficiary” means any beneficiary which is an organization described in section 170(c). (ii) ESOP beneficiary The term “ESOP beneficiary” means any beneficiary which is an employee stock ownership plan (as defined in section 4975(e)(7)) that holds a remainder interest in qualified employer securities (as defined in section 664(g)(4)) to be transferred to such plan in a qualified gratuitous transfer (as defined in section 664(g)(1)). (iii) Qualified charitable remainder trust The term “qualified charitable remainder trust” means a charitable remainder annuity trust or a charitable remainder unitrust (described in section 664).

(9) Denial of double deduction Nothing in this section or any other provision of this chapter shall allow the value of any interest in property to be deducted under this chapter more than once with respect to the same decedent.

(10) Specific portion For purposes of paragraphs (5), (6), and (7)(B)(iv), the term “specific portion” only includes a portion determined on a fractional or percentage basis.

For purposes of this section, an interest in property shall be considered as passing from the decedent to any person if and only if—

(1) such interest is bequeathed or devised to such person by the decedent;

(2) such interest is inherited by such person from the decedent;

(3) such interest is the dower or curtesy interest (or statutory interest in lieu thereof) of such person as surviving spouse of the decedent;

(4) such interest has been transferred to such person by the decedent at any time;

(5) such interest was, at the time of the decedent’s death, held by such person and the decedent (or by them and any other person) in joint ownership with right of survivorship;

(6) the decedent had a power (either alone or in conjunction with any person) to appoint such interest and if he appoints or has appointed such interest to such person, or if such person takes such interest in default on the release or nonexercise of such power; or

(7) such interest consists of proceeds of insurance on the life of the decedent receivable by such person.

Except as provided in paragraph (2), if the surviving spouse of the decedent is not a citizen of the United States—

Except as provided in paragraph (2), if the surviving spouse of the decedent is not a citizen of the United States—

(A) no deduction shall be allowed under subsection (a), and

(B) section 2040(b) shall not apply.

If any property passes from the decedent to the surviving spouse of the decedent, for purposes of subparagraph (A), such property shall be treated as passing to such spouse in a qualified domestic trust if—

(A) In general Paragraph (1) shall not apply to any property passing to the surviving spouse in a qualified domestic trust.

(B) Special ruleIf any property passes from the decedent to the surviving spouse of the decedent, for purposes of subparagraph (A), such property shall be treated as passing to such spouse in a qualified domestic trust if— (i) such property is transferred to such a trust before the date on which the return of the tax imposed by this chapter is made, or (ii) such property is irrevocably assigned to such a trust under an irrevocable assignment made on or before such date which is enforceable under local law.

If—

(A) property passes to the surviving spouse of the decedent (hereinafter in this paragraph referred to as the “first decedent”),

(B) without regard to this subsection, a deduction would be allowable under subsection (a) with respect to such property, and

(C) such surviving spouse dies and the estate of such surviving spouse is subject to the tax imposed by this chapter,

Paragraph (1) shall not apply if—

(A) the surviving spouse of the decedent becomes a citizen of the United States before the day on which the return of the tax imposed by this chapter is made, and

(B) such spouse was a resident of the United States at all times after the date of the death of the decedent and before becoming a citizen of the United States.

In the case of any property with respect to which a deduction would be allowable under subsection (a) but for this subsection, the determination of whether a trust is a qualified domestic trust shall be made—

(A) In generalIn the case of any property with respect to which a deduction would be allowable under subsection (a) but for this subsection, the determination of whether a trust is a qualified domestic trust shall be made— (i) as of the date on which the return of the tax imposed by this chapter is made, or (ii) if a judicial proceeding is commenced on or before the due date (determined with regard to extensions) for filing such return to change such trust into a trust which is a qualified domestic trust, as of the time when the changes pursuant to such proceeding are made.

(B) Statute of limitations If a judicial proceeding described in subparagraph (A)(ii) is commenced with respect to any trust, the period for assessing any deficiency of tax attributable to any failure of such trust to be a qualified domestic trust shall not expire before the date 1 year after the date on which the Secretary is notified that the trust has been changed pursuant to such judicial proceeding or that such proceeding has been terminated.

(Aug. 16, 1954, ch. 736, 68A Stat. 392; Pub. L. 89–621, § 1(a), Oct. 4, 1966, 80 Stat. 872; Pub. L. 94–455, title XIX, § 1902(a)(12)(A), title XX, §§ 2002(a), 2009(b)(4)(D), (E), Oct. 4, 1976, 90 Stat. 1805, 1854, 1894; Pub. L. 95–600, title VII, § 702(g)(1), (2), Nov. 6, 1978, 92 Stat. 2930; Pub. L. 97–34, title IV, § 403(a)(1), (d)(1), Aug. 13, 1981, 95 Stat. 301, 302; Pub. L. 97–448, title I, § 104(a)(2)(A), (8), Jan. 12, 1983, 96 Stat. 2380, 2381; Pub. L. 98–369, div. A, title X, § 1027(a), July 18, 1984, 98 Stat. 1031; Pub. L. 100–647, title V, § 5033(a)(1), title VI, § 6152(a), Nov. 10, 1988, 102 Stat. 3670, 3725; Pub. L. 101–239, title VII, § 7815(d)(4)(A), (5), (6), (8), 7816(q), Dec. 19, 1989, 103 Stat. 2415, 2416, 2423; Pub. L. 101–508, title XI, §§ 11701(l)(1), 11702(g)(5), Nov. 5, 1990, 104 Stat. 1388–513, 1388–516; Pub. L. 102–486, title XIX, § 1941(a), Oct. 24, 1992, 106 Stat. 3036; Pub. L. 105–34, title XIII, § 1311(a), title XV, § 1530(c)(8), Aug. 5, 1997, 111 Stat. 1044, 1078.)