Preferential tariff treatment after importation allows late claims, supporting refunds of excess duties with documentary proof. Late claims for preferential tariff treatment may be made after importation, and excess duties are refundable where the goods would have qualified at importation. The importer must make the claim under rule 16 and provide required importation documents, including an origin declaration if relied on. A late claim must be filed within one year of importation, unless a longer period is allowed by the importing Party's laws and regulations.