Gst refund on export of software services

Dear Experts, seek your advice on the following query on Refund of Input credit relating to export of service. (1) What are the supporting documenst to be submitted for getting gst input credit for export of service (2) Is there any certificate which required from bank to prove the realisation of the export proceeds (3) If so, what is the procedure for getting certificate from bank (4) Is there any format for the bank certificate...Kindly give your valuable reply