Rate of exchange for GST valuation set by customs for goods and accounting principles for services; export invoice and return rules updated. The amendment revises GST rules: it prescribes customs-notified exchange rates for goods and accounting-principle rates for services for valuation; mandates specific export invoice endorsements and limited recipient/delivery/destination details; permits the Commissioner to require electronic FORM GSTR-3B filing when GSTR-1/GSTR-2 deadlines are extended and directs electronic generation of FORM GSTR-3 (Part A from GSTR-1/GSTR-2 and prior liabilities; Part B from GSTR-3B) with reconciliation and credit ledger adjustment for excess input tax credit; and updates HSN column headings in TRAN forms.