Customs tariff schedule amendments update the First Schedule through phased modifications and deferred effective dates. The First Schedule to the Customs Tariff Act, 1975 is amended through the Second Schedule and the Third Schedule, with additional amendments taking effect from 1 May 2026 through the Fourth Schedule and the Fifth Schedule. The provision establishes a staged schedule-based revision of tariff entries, with one set of changes linked to commencement of the Finance Act, 2026 and another expressly deferred to a later effective date.