GST notification amendment updates HSN classification and adds Diethylcarbamazine to List 1 under GST law, effective immediately. The Tamil Nadu GST notification is amended to substitute the Schedule I entry for S. No.259A with '9503' and to insert 'Diethylcarbamazine' as a new serial in List 1; the amendment is issued under the Act and takes effect from 2 June 2021.