GST DEBIT NOTE CREDIT NOTE

Please  refer  section 34 of the CGST act  2017  . Only supplier can issue Debit Note -Credit Note under GST act  for reason specified  in section 34  of the CGST act . How  recipient  will file GSTR 1 , Not  possible . GSTR 1 is for  Outward supply .      

If the adjust leads to increase in purchase and therefore increase in ITC, then you need to request the Supplier to issue you a Debit Note (credit note for you) so that ITC is captured in his R1 filing and thus in your 2A.

If the adjustment reduces your purchase value and therefore your ITC, you can still request supplier to issue a credit note to you. But if he is Not ready to issue the Credit Note and you are going to adjust the difference in your payment then, you can raise a Debit Note in your books and reduce your ITC in GSTR-3B to the extent of the difference.