Rate of exchange clarified under GST amendment; export invoicing and GSTR-3B return process and credit adjustments prescribed. The amendment prescribes staggered commencement dates, substitutes rule 34 to fix exchange rate determination-customs-notified rates for goods and GAAP-based rates for services at time of supply-and revises export invoice endorsements. It permits use of FORM GSTR-3B when GSTR-1/GSTR-2 deadlines are extended; FORM GSTR-3 will be auto-generated with PART A from returns and liabilities and PART B from GSTR-3B, allowing registrants to reconcile discrepancies and credit any excess input tax to the electronic credit ledger. Minor wording and form-heading changes are also made.