I have to update GSTR-1 for FY 2020-2021, the last date for the same was 11 October, 2021, bt I filed return for the month of September without that amendment. is there any other way to do so or I should update that in the October's return ??
No , as per CGST act 2017 , amendment can be done only before due date of the return for the month of September 21 or date of annual return which ever is earlier .