(a) Every common carrier by rail which is required by the act to regulate commerce to file with the Board any tariff or schedule of rates, fares, or charges, or any concurrence in such tariff or schedule, shall be required to keep operating accounts and to file an annual operating report unless specifically excused by the Board.

(b) Every railway corporation owning but not operating a railway used in interstate or foreign commerce shall be required to file with the Board an annual nonoperating report unless relieved therefrom under the provisions of rule following.

(c) Any actually existing inactive corporation coming within the scope of rule given above may be relieved from the requirements of that rule if it has no outstanding stocks or obligations not held by or for its controlling corporation and the controlling corporation reports for the inactive corporation such facts as the Board may require to be reported.

(d) Reports of a controlling corporation and its controlled corporations must exclude duplications in respect of investments in railway plant and equipment and in respect of securities outstanding.