The department may, upon application made to it, in such form as it shall prescribe, on or prior to the last day for filing any annual report, and upon proper cause shown, grant to the corporation, required to file such report, an extension of not more than sixty days within which such report may be filed. If the Federal income tax authorities grant an extension of time for filing the reports with the Federal Government, the department shall automatically grant an extension of time for filing the annual report under this article until the fifteenth day of the month following the termination of the Federal extension, but the amount of tax due shall, in such cases, nevertheless, be subject to interest from the due dates and at the rates fixed by this article.