Exchange rate for valuation of goods and services set; procedural changes for returns, input tax credit and export invoices. Amendments modify compliance timelines and valuation methodology, prescribing the notified Customs exchange rate for goods and accounting principles rates for services at time of supply, require separate input tax credit determination by tax type, impose specific export invoice endorsements and particulars, and empower the Commissioner to mandate FORM GSTR-3B where GSTR-1/GSTR-2 deadlines are extended with electronic generation and adjustment procedures for FORM GSTR-3 and crediting of excess input tax to the electronic credit ledger.