Retrospective amendment power affirmed for central government to modify GST notification, validating past retrospective changes. The provision deems a specified ministerial notification under the Union Territory Goods and Services Tax framework to be amended retrospectively as set out in the Eighth Schedule and effective from the dates therein, and further deems the Central Government to have had the authority to make such retrospective amendments under the relevant Union Territory and Central Goods and Services Tax enactments at all material times.