Rate of exchange for GST clarifies valuation for goods and services and adjusts invoice and return reconciliation procedures. The amendment prescribes that the rate of exchange for goods valuation follows the rate notified under the Customs Act for the time of supply, while services valuation follows rates determined under generally accepted accounting principles for the time of supply. It requires separate determination of input tax credit for central, State/Union territory and integrated tax, permits estimation of credit for inputs held in stock based on prevailing market price where invoices are absent, and mandates specified export invoice endorsements and particulars in place of certain earlier requirements.