Except as otherwise provided in RCW 83.110A.050 and 83.110A.060, the following rules apply to credits and deferrals of estate taxes:
(1) A credit resulting from the payment of gift taxes or from estate taxes paid on property previously taxed inures ratably to the benefit of all persons to which the estate tax is apportioned.(2) A credit for state or foreign estate taxes inures ratably to the benefit of all persons to which the estate tax is apportioned, except that the amount of a credit for a state or foreign tax paid by a beneficiary of the property on which the state or foreign tax was imposed, directly or by a charge against the property, inures to the benefit of the beneficiary.(3) If payment of a portion of an estate tax is deferred because of the inclusion in the gross estate of a particular interest in property, the benefit of the deferral inures ratably to the persons to which the estate tax attributable to the interest is apportioned. The burden of any interest charges incurred on a deferral of taxes and the benefit of any tax deduction associated with the accrual or payment of the interest charge is allocated ratably among the persons receiving an interest in the property.