(a) Except as otherwise provided in subsection (c) of this section, the following rules apply:

(1) To the extent that a provision of a decedent’s will specifically indicates an intent to direct the apportionment of an estate tax, the tax must be apportioned accordingly.

(2) Any portion of an estate tax not apportioned pursuant to paragraph (a)(1) of this section must be apportioned in accordance with any provision of a revocable trust of which the decedent was the settlor which specifically indicates an intent to direct the apportionment of an estate tax. If conflicting apportionment provisions appear in 2 or more revocable trust instruments, the provision in the most recently dated instrument prevails. For purposes of this paragraph:

a. A trust is revocable if it was revocable immediately after the trust instrument was executed, even if the trust subsequently becomes irrevocable; and

b. The date of an amendment to a revocable trust instrument is the date of the amended instrument only if the amendment contains an apportionment provision.

(3) If any portion of an estate tax is not apportioned pursuant to paragraph (a)(1) or (2) of this section, and a provision in any other dispositive instrument specifically directs that any interest in the property disposed of by the instrument is or is not to be applied to the payment of the estate tax attributable to the interest disposed of by the instrument, the provision controls the apportionment of the tax to that interest.

(b) Subject to subsection (c) of this section, and unless the decedent in a will or revocable trust specifically indicates an intent to waive the application of this statute, the following rules apply:

(1) If an apportionment provision directs that a person receiving an interest in property under an instrument is to be exonerated from the responsibility to pay an estate tax that would otherwise be apportioned to the interest,

a. The tax attributable to the exonerated interest must be apportioned among the other persons receiving interests passing under the instrument, or

b. If the values of the other interests are less than the tax attributable to the exonerated interest, the deficiency must be apportioned ratably among the other persons receiving interests in the apportionable estate that are not exonerated from apportionment of the tax.

(2) If an apportionment provision directs that an estate tax is to be apportioned to an interest in property a portion of which qualifies for a marital or charitable deduction, the estate tax must first be apportioned ratably among the holders of the portion that does not qualify for a marital or charitable deduction and then apportioned ratably among the holders of the deductible portion to the extent that the value of the nondeductible portion is insufficient.

(3) Except as otherwise provided in paragraph (b)(4) of this section, if an apportionment provision directs that an estate tax be apportioned to property in which 1 or more time-limited interests exist, other than interests in specified property under § 2907 of this title, the tax must be apportioned to the principal of that property, regardless of the deductibility of some of the interests in that property.

(4) If an apportionment provision directs that an estate tax is to be apportioned to the holders of interests in property in which 1 or more time-limited interests exist and a charity has an interest that otherwise qualifies for an estate tax charitable deduction, the tax must first be apportioned, to the extent feasible, to interests in property that have not been distributed to the persons entitled to receive the interests. No tax shall be paid from a charitable remainder annuity trust or a charitable remainder unitrust described in § 664 of the Internal Revenue Code [26 U.S.C. § 664] and created during the decedent’s life.

(c) A provision that apportions an estate tax is ineffective to the extent that it increases the tax apportioned to a person having an interest in the gross estate over which the decedent had no power to transfer immediately before the decedent executed the instrument in which the apportionment direction was made. For purposes of this subsection, a testamentary power of appointment is a power to transfer the property that is subject to the power.

79 Del. Laws, c. 159, § 1.