21A. Any reference in this Act to the Income tax Act, 1922, shall, in relation to the profits of any chargeable accounting period and to the state of affairs and all the circumstances necessary to determine the charge to excess profits tax, mean the said Act as in force in the relevant period: Provided that whatever be the relevant period, references to section 46 of the said Act shall be deemed to include references to sub sections (8), (9) and (10) of that section.