Retrospective tax change: exemption for fishmeal and reduced central tax on agricultural machinery parts; no refunds. The amendment retrospectively exempts central tax on supply of fishmeal for a specified historical period and retrospectively levies central tax at a reduced rate on pulleys, wheels and other parts (heading 8483) when used as parts of agricultural machinery (headings 8432, 8433 and 8436) for a specified historical period; it further provides that taxes already collected for those periods shall not be refunded.