Exemption eligibility narrowed: units performing peripheral activities excluded and required to file quarterly returns with commissioner. Amendments exclude units performing only peripheral processes-such as packing, re packing, labeling, re labeling, and alteration of retail sale price-from exemption under notification Nos. 49 & 50/2003-CE, requiring such units to pay duty normally. Concurrently, rule 12 was amended to mandate a quarterly return (Form A) for units availing the exemption, to be filed with the Commissioner by the twentieth day of the month following the quarter, electronically or by post; the obligation covers both existing and future units.