Wrong Filing of Credit Note in GSTR 1 & GSTR 3B

Make amendment and pay tax, then it will be shown in annual return of 2019-20

You can rectify this mistake by amending Credit Note through Credit Note amendments column in Current month GSTR 1, As Credit Note was not issued..Put value as Zero in credit note through Amendments Column.

In GSTR 3B you can reverse that in current month return..Add amount of credit note in output Column as earlier you deducted this from output, and pay tax accordingly.

You can update it in the current month. Please add such amount in your liability and pay interest on the same