Sec. 6. (a) If proceedings have not been instituted under this chapter to determine the inheritance tax imposed on the decedent's transfer of a contingent or defeasible future interest in property or if the tax imposed on such a transfer is postponed under subsection (b), the department of state revenue shall, notwithstanding the provisions of IC 6-4.1-5, appraise the property interest at its fair market value when the transferee of the interest obtains the beneficial enjoyment or possession of the property.
(b) The inheritance tax imposed on the decedent's transfer of a contingent or defeasible interest in property accrues and is due when the transferee of the interest obtains the beneficial enjoyment or possession of the property if the fair market value of the property interest as of the appraisal date prescribed by IC 6-4.1-5-1.5 cannot otherwise be ascertained under this chapter.