Unlimited Marital Deduction

§ 2523. Gift to spouse(a) Allowance of deductionWhere a donor transfers during the calendar year by gift an interest in property to a donee who at the time of the gift is the donor’s spouse, there shall be allowed as a deduction in computing taxable gifts for the calendar year an amount with respect to such interest equal to its value. (b) Life estate or other terminable interestWhere, on the lapse of time, on the occurrence of an event or contingency, or on the failure of an event or contingency to occur, such interest transferred to the spouse will terminate or fail, no deduction shall be allowed with respect to such interest—(1) if the donor retains in himself, or transfers or has transferred (for less than an adequate and full consideration in money or money’s worth) to any person other than such donee spouse (or the estate of such spouse), an interest in such property, and if by reason of such retention or transfer the donor (or his heirs or assigns) or such person (or his heirs or assigns) may possess or enjoy any part of such property after such termination or failure of the interest transferred to the donee spouse; or (2) if the donor immediately after the transfer to the donee spouse has a power to appoint an interest in such property which he can exercise (either alone or in conjunction with any person) in such manner that the appointee may possess or enjoy any part of such property after such termination or failure of the interest transferred to the donee spouse. For purposes of this paragraph, the donor shall be considered as having immediately after the transfer to the donee spouse such power to appoint even though such power cannot be exercised until after the lapse of time, upon the occurrence of an event or contingency, or on the failure of an event or contingency to occur. An exercise or release at any time by the donor, either alone or in conjunction with any person, of a power to appoint an interest in property, even though not otherwise a transfer, shall, for purposes of paragraph (1), be considered as a transfer by him. Except as provided in subsection (e), where at the time of the transfer it is impossible to ascertain the particular person or persons who may receive from the donor an interest in property so transferred by him, such interest shall, for purposes of paragraph (1), be considered as transferred to a person other than the donee spouse. (c) Interest in unidentified assetsWhere the assets out of which, or the proceeds of which, the interest transferred to the donee spouse may be satisfied include a particular asset or assets with respect to which no deduction would be allowed if such asset or assets were transferred from the donor to such spouse, then the value of the interest transferred to such spouse shall, for purposes of subsection (a), be reduced by the aggregate value of such particular assets.