Customs duty exemption powers allow general notifications, special orders, and conditional relief subject to statutory duty limits. Section 25 of the Customs Act, 1962 empowers the Central Government to exempt specified goods from customs duty in the public interest by general notification or by special order in exceptional cases, subject to conditions and stated circumstances. The provision also allows clarificatory explanations to exemption notifications or orders, alternative forms or methods of levy subject to the statutory duty ceiling, and immediate effectiveness of notifications unless otherwise provided. It further regulates the duration of conditional exemptions, excludes specified categories, bars collection of duty of one hundred rupees or less, and contains a deeming exemption for certain mineral oils imported before 7 February 2002.