(a) The following persons shall make a return:(1) The personal representative of the estate of the decedent as to property of the decedent administered by him and additional property which is or may be subject to inheritance tax of which he shall have or acquire knowledge.(2) The transferee of property upon the transfer of which inheritance tax is or may be imposed by this article, including a trustee of property transferred in trust. No separate return need be made by the transferee of property included in the return of a personal representative.(b) The inclusion of property in the return shall not constitute an admission that its transfer is taxable.(c) Any person required to file a return under subsection (a) shall promptly file a supplemental return with respect to additional assets and transfers which come to his knowledge after the original return has been filed.(d) The returns required by subsection (a) shall be filed within nine months after the death of the decedent. At any time prior to the expiration of the nine-month period, the department, in its discretion, may grant an extension of the time for filing a return for an additional period of six months.(e) The returns required by subsections (a) and (c) shall be made in the form prescribed by the department.(f) When the decedent was a resident, the returns shall be filed with the register. When the decedent was a nonresident, the returns shall be filed with the register who issued letters, if any, in this Commonwealth; otherwise, the returns shall be filed with the department.1971, March 4, P.L. 6, No. 2, Art. XXI, § 2136, added 1991, Aug. 4, P.L. 97, No. 22, § 36, effective in 60 days.