§ 13. "That there may be included in any Act of the present Session relating to finance such amendments of Section twenty-one of the Finance Act, 1922 (which relates to Surtax on the undistributed income of pertain companies), and of the enactments relating to or amending that Section, as Parliament may determine, and any such Act may provide that the said amendments shall have effect for the purpose of assessment to Surtax for the year 1935–36 and subsequent years."