The relevant portion of Section 11A provid ed. "(1) When any duty of excise has not been levied or paid or has been short levied or short paid or erroneously refunded, a Central Excise Officer may, within six months from the relevant date, serve notice on the person chargeable with the duty which has not been levied or paid or which has been short levied or short paid or to whom the refund has erro neously been made, requiring him to show cause why he should not pay the amount specified in the notice: (2) The Assistant Collector of Central Excise shall, after considering the representation, if any, made by the person on whom notice is served under sub section (1), determine the amount of duty of.excise due from such person (not being in excess of the amount specified in the notice) and thereupon such person shall pay the amount so determined. ' ' Reference to Section 3 of the Act which contains the charg ing provision clearly shows that levy and collection are two distinct and separate 313 steps.