Validation of retrospective classification: notification deemed effective earlier, enabling refundable antidumping duty claims within a limited period. A notification amending a prior tariff-classification notification is deemed to have been validly in force from the earlier notification date for all purposes, thereby affecting antidumping classification. Antidumping duty collected that would not have been levied if the amendment had been in force is refundable, and refund claims must be made within a limited period measured from the assent to the Finance Bill.