Login to GST Website ---->>> Services--->> User Services--->> Refund--->> select the type of refund you want to avail( your Question is silent)----->> Select the month---Keep the records/Workings in PDF format-----upload---->> Enter Bank Account Number already registerd with GST .
this is normal procedure, but you if have a specific request like EOU/Exports then you must have Endorsement of Invoice, Shipping bill Etc
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