Payment of igst using sgst credits

Export is Zero rated supply  in GST law  , When  you paying  IGST  for export   it is refundable amount  ,you can apply for refund .

There are 2 types of zero-rated supply-With payment and without payment. In the given case export is done with payment and thus you can utilise the CGST & SGST credit for paying IGST. Then you can claim the refund of IGST paid.