GENERAL APPORTIONMENT OF ESTATE TAX; EXCEPTIONS.

(a) A representative shall charge each person interested in the estate a portion of the total estate tax assessed against the estate. The portion charged to each person must represent the same ratio as the taxable value of that person's interest in the estate included in determining the amount of the tax bears to the total taxable value of all the interests of all persons interested in the estate included in determining the amount of the tax. In apportioning an estate tax under this subsection, the representative shall disregard a portion of the tax that is:

(1) apportioned under the law imposing the tax;

(2) otherwise apportioned by federal law; or

(3) apportioned as otherwise provided by this subchapter.

(b) Subsection (a) does not apply to the extent the decedent, in a written inter vivos or testamentary instrument disposing of or creating an interest in property, specifically directs the manner of apportionment of estate tax or grants a discretionary power of apportionment to another person. A direction for the apportionment or nonapportionment of estate tax is limited to the estate tax on the property passing under the instrument unless the instrument is a will that provides otherwise.

(c) If directions under Subsection (b) for the apportionment of an estate tax are provided in two or more instruments executed by the same person and the directions in those instruments conflict, the instrument disposing of or creating an interest in the property to be taxed controls. If directions for the apportionment of estate tax are provided in two or more instruments executed by different persons and the directions in those instruments conflict, the direction of the person in whose estate the property is included controls.

(d) Subsections (b) and (c) do not:

(1) grant or enlarge the power of a person to apportion estate tax to property passing under an instrument created by another person in excess of the estate tax attributable to the property; or

(2) apply to the extent federal law directs a different manner of apportionment.