Credit or Debit note to be issued.

Hi,

I am a vendor .

Invoice has been entered in August 21 GST 1 and by mistake the same invoice was entered in September 21 GST 1 .  Example : Invoice no 64 / 0821 in August &  invoice no 640821 In Sept.

GST has been filed for July - Sept Qtr.. The GST has been paid twice for same invoice in August & September 21. . How to rectify the situation?

I have been suggested to issue Credit note to the client & file it in  March GST 1. Please let know if it is correct step.

My confusion is whether i should issue Credit note or Debit note to client and file it accordingly in GST 1 -   since i have made double GST payment in 3 B for same invoice [with variation in invoice numbering]

Please suggest along with reasons.

Thank you.