(a) Any additional assessment or estimated assessment shall be made by the department within five years of the date when the annual return required by section three hundred four¹ hereof should have been filed, as prescribed in this act, whether the date originally prescribed or pursuant to any extensions of the time for filing such return duly granted by the department and not after. Any such additional assessment or estimated assessment may be made at any time during such period, notwithstanding that the department may have made one or more previous additional assessments or estimated assessments or both against the taxpayer for the year in question or for any part of such year. In any such case, no credit shall be given for any penalty previously assessed or paid.

(b) If the taxpayer shall have died, any taxes, interest and penalties due under this act for years prior to his death or for the year of his death and whether based on original assessments, additional or estimated assessments or otherwise, may be presented by the department at audit of his estate in the orphans’ court. Such court shall give full effect to the priorities and equitable interest given to the Commonwealth by this act.