4Where any sum is paid to the principal company for, or on account of, a post-war refund, the undertakings and authorities required by Part IV of this Act in relation to the payment shall not require the approval of the advisory panel by reason of the fact that the trade or business specified in those undertakings and authorities is not the original trade or business if the trade or business so specified is being or is to be carried on by a subsidiary member of the group.