(1) As used in this section, unless the context otherwise requires:

(a) "Advanced fraction" means a fraction that has as its numerator the amount of the advanced tax and as its denominator the value of the interests in insulated property to which that tax is attributable.

(b) "Advanced tax" means the aggregate amount of estate tax attributable to interests in insulated property that is required to be advanced by uninsulated holders under subsection (3) of this section.

(c) "Insulated property" means property subject to a time-limited interest that is included in the apportionable estate but is unavailable for payment of an estate tax because of impossibility or impracticability.

(d) "Uninsulated holder" means a person who has an interest in uninsulated property.

(e) "Uninsulated property" means property included in the apportionable estate, other than insulated property.

(2) If estate tax is to be advanced pursuant to subsection (3) of this section by persons holding interests in uninsulated property subject to a time-limited interest other than property to which section 15-12-1407 applies, the estate tax shall be advanced, without further apportionment, from the principal of the uninsulated property.

(3) Subject to sections 15-12-1409 (2) and 15-12-1409 (4), an estate tax attributable to interests in insulated property shall be advanced ratably by uninsulated holders. If the value of an interest in uninsulated property is less than the amount of estate taxes otherwise required to be advanced by the holder of that interest, the deficiency shall be advanced ratably by the person holding interests in any property that is excluded from the apportionable estate as defined in section 15-12-1402 (1)(b) as if those interests were in uninsulated property.

(4) A court having jurisdiction to determine the apportionment of an estate tax may require a beneficiary of an interest in insulated property to pay all or part of the estate tax otherwise apportioned to the interest if the court finds that it would be substantially more equitable for that beneficiary to bear the tax liability personally than for that part of the tax to be advanced by uninsulated holders.

(5) When a distribution of insulated property is made, each uninsulated holder may recover from the distributee a ratable portion of the advanced fraction of the property distributed. To the extent that undistributed insulated property ceases to be insulated, each uninsulated holder may recover from the property a ratable portion of the advanced fraction of the total uninsulated property.

(6) Upon a distribution of insulated property for which the distributee becomes obligated to make a payment to uninsulated holders pursuant to subsection (4) of this section, a court may award an uninsulated holder a recordable lien on the distributee's property to secure the distributee's obligation to that uninsulated holder.