Export goods returned for repair

We had exported a consignment on payment of IGST. Now buyer have returned these goods for repair. We cleared these goods from customs with NIL GST under customs bond as we will be re-exporting the goods within 6 months as per customs Notification # 158/95 dtd 14/11/95.

Do we need to reverse the IGST in the credit note or just simple entry with Cr to Buyer and Dr to sales?