(1) The personal representative of every estate subject to the tax imposed by sections 77-2101 to 77-2116 shall file with the Tax Commissioner within twelve months from the date of death of the decedent:

(a) An estate tax return on forms prescribed by the Tax Commissioner for taxes due under such sections;

(b) A true copy of any federal estate tax return, pages 1, 2, and 3;

(c) A true copy of the federal determination of estate tax whether issued by the Internal Revenue Service or a federal court, if any. If such determination has not been received from the Internal Revenue Service or the federal court at the time of filing the return required in subdivision (a) of this subsection, a statement that the determination is unavailable shall be attached to the return and a true copy of the federal determination shall be filed with the Tax Commissioner within ten days of receipt of such determination by the personal representative; and

(d) A true copy of the inheritance tax return or worksheet as filed with the county court in each county where the decedent had property.

(2) For the generation-skipping transfer tax, a return in the form required by the Tax Commissioner shall be filed with the Tax Commissioner within twelve months of the date of the transfer by the transferee. The return shall include a true copy of the federal generation-skipping transfer tax return and the federal determination of the federal generation-skipping transfer tax due whether issued by the Internal Revenue Service or a federal court, if any.