GST Rule Amendments update exchange rate rules, export invoice endorsements and the GSTR-3B provisional return process. The amendment substitutes Rule 34 to prescribe exchange rates for valuation-Customs Board rate for goods at time of supply and generally accepted accounting principles for services at time of supply-and revises invoicing and return procedures: export invoices must carry specified endorsements and recipient/destination details, and where GSTR filing deadlines are extended the Commissioner may require FORM GSTR-3B electronically, with electronic generation and reconciliation of Parts A and B of FORM GSTR-3 and crediting of any excess input tax to the electronic credit ledger.