The assessor shall determine the amount of tax due and payable under this chapter upon any estate or part of that estate. If, after determination and certification of the full amount of the tax upon an estate or any interest in or part of an estate, the estate receives or becomes entitled to property in addition to that shown in the estate tax return filed with the assessor or the United States Internal Revenue Service changes any item increasing the estate's liability shown in the Maine estate tax return filed with the assessor, the personal representative shall within 180 days of any receipt, entitlement or change file an amended Maine estate tax return. The assessor shall determine the amount of additional tax and shall certify the amount due, including interest and penalties, to the person by whom the tax is payable.   [PL 2011, c. 380, Pt. M, §9 (NEW).]