(b) It shall be the duty of each corporation liable to pay tax under this article to pay estimated tax under section 3003.2¹ and to make final payment of tax due for the taxable year with the annual report required by this section.

(c) The amount of all taxes, imposed under the provisions of this article, not paid on or before the times as above provided, shall bear interest as provided in section 806 of the act of April 9, 1929 (P.L. 343, No. 176),² known as “The Fiscal Code,” from the date they are due and payable until paid, except that if the taxable income has been, or is increased by the Commissioner of Internal Revenue, or by any other agency or court of the United States, interest shall be computed on the additional tax due from thirty days after the corporation receives notice of the change of income until paid: Provided, however, That any corporation may pay the full amount of such tax, or any part thereof, together with interest due to the date of payment, without prejudice to its right to present and prosecute, an administrative petition or an appeal to court. If it be thereafter determined that such taxes were overpaid, the department shall enter a credit to the account of such corporation, which may be used by it in the manner prescribed by law.

(d) If the officers of any corporation shall neglect, or refuse to make any report as herein required, or shall knowingly make any false report, a penalty of five hundred dollars ($500) plus an additional one per cent for every dollar of tax determined to be due in excess of twenty-five thousand dollars ($25,000) shall be added to the tax determined to be due. No amounts added to the tax shall bear any interest whatsoever.

(e) If any corporation closes its fiscal year not upon December 31, but upon some other date, and reports to the Federal Government as of such other date, or would so report were it to make a return to the Federal Government, such corporation shall certify such fact to the department, and shall make the annual report, herein required, on or before the fifteenth day of the month following the due date of the return to the Federal Government, or would be due were it to be required of such corporation, subject in all other respects to the provisions of this article.

(f) If the corporation shall claim in its report that the return made to the Federal Government was inaccurate, the amount claimed by it to be the taxable income, taxable under this article, and the basis of such claim of inaccuracy, shall be fully specified.