4. (1) The Government may make rules for the purpose of regulating the transaction of business by the Board, and every order made or act done in accordance with such rules shall be deemed to be the order or act, as the case may be, of the National Board of Revenue. (2) Any rules under clause (1) may be made so as to be retrospective from any date not earlier than the commencement of this Order and such rules may also validate any acts done or orders made by, or any proceedings of the National Board of Revenue or its Chairman or any of its Members or Officers before the making of such rules which, if done, made or taken after the commencement of those rules, would not be inconsistent therewith. (3) No act, order or proceeding validated under clause (2) shall be called in question merely on the ground that such act, order or proceeding was not valid at the time when it was done, made or taken.