(1) Except as otherwise provided in subsection (3) of this section, the following rules apply:

(a) To the extent that a provision of a decedent's will provides for the apportionment of an estate tax, the tax must be apportioned accordingly.

(b) Any portion of an estate tax not apportioned pursuant to (a) of this subsection must be apportioned in accordance with any provision of a revocable trust of which the decedent was the settlor which provides for the apportionment of an estate tax. If conflicting apportionment provisions appear in two or more revocable trust instruments, the provision in the most recently dated instrument prevails. For purposes of this subsection (1)(b):

(i) A trust is revocable if it was revocable immediately after the trust instrument was executed, even if the trust subsequently becomes irrevocable; and

(ii) 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.

(c) If any portion of an estate tax is not apportioned pursuant to (a) or (b) of this subsection, and a provision in any other dispositive instrument provides 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.

(2) Subject to subsection (3) of this section, and unless the decedent provides to the contrary, the following rules apply:

(a) If an apportionment provision provides 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:

(i) The tax attributable to the exonerated interest must be apportioned among the other persons receiving interests passing under the instrument; or

(ii) 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.

(b) If an apportionment provision provides 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.

(c) Except as otherwise provided in (d) of this subsection, if an apportionment provision provides that an estate tax be apportioned to property in which one or more time-limited interests exist, other than interests in specified property under RCW 83.110A.060, the tax must be apportioned to the principal of that property, regardless of the deductibility of some of the interests in that property.

(d) If an apportionment provision provides that an estate tax is to be apportioned to the holders of interests in property in which one 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 section 664 of the internal revenue code and created during the decedent's life.

(e) Persons receiving tangible personal property as defined in RCW 11.12.260 by specific gifts pursuant to the provisions of a will or revocable trust or by right of survivorship , are exonerated from apportionment of estate tax up to an aggregate value of property permitted to pass by affidavit for small estates pursuant to RCW 11.62.010(2)(c).

(f) Persons receiving specific pecuniary gifts pursuant to the provisions of a will or revocable trust are exonerated from apportionment of estate tax up to an aggregate amount of money equal to one-half of the value of property permitted to pass by affidavit for small estates pursuant to RCW 11.62.010(2)(c).

(g) If persons receive an aggregate value of tangible personal property or the amount of money in excess of the ceiling allowed to be exonerated for apportionment for estate taxes for that type of property, the portion of each gift to be exonerated is the maximum amount of money or value of tangible personal property that is allowed to be exonerated multiplied by the proportion of money received by each person over the amount of money received by all persons, or the value of tangible personal property received by each person over the value of all tangible personal property received by all persons.

(3) 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 section, a testamentary power of appointment is a power to transfer the property that is subject to the power.