306 Ascertainment of value of certain interests
If it is necessary for the purpose of assessing duty under this Act to ascertain the value of:
(a) any estate or annuity or interest for the life of any person, or
(b) any estate or annuity or interest determinable on or subject to any contingency or the happening of any event, or
(c) any estate or annuity or interest in remainder expectant on the death of any person or expectant on or subject to any contingency or the happening of any event,
regard may be had in ascertaining the value of any such property to the death of the person having the life estate or annuity or interest or the happening of the contingency or event at any time before the assessment of duty is actually made.