Recovery of duty: non compliance with concessional import conditions triggers bond based recovery of duty difference with interest. Where a manufacturer who availed a concessional import exemption fails to use imported goods as required or fails to take action under rule 7, the appropriate Central Excise officer may invoke the bond and recover the difference between duty leviable but for the exemption and that already paid, together with interest at the notified rate for the period from the date of importation until actual payment of the entire duty difference.