Input tax credit and return compliance rules are tightened under West Bengal GST, with retrospective notification changes and selective tax relief. The Act introduces tax deduction at source for profession tax, revises penalty and renewal provisions, and amends the transport infrastructure fund law and the West Bengal Goods and Services Tax Act, 2017. The GST amendments cover input tax credit, outward and inward supply reporting, return filing, reversal of credit, interest, payment through the electronic credit ledger, and refund rules. It also gives retrospective effect to specified GST notifications and creates a retrospective exemption for unintended waste generated in fish meal production, while barring refunds of tax already collected.