Agreed with Mr jatin. But now there is no way for paying late fee in gst portal currently. Everyone should file GSTR 1 before the due date otherwise in future date late fee may be arised.
***Why not You / We calculate the Late fee and Pay it with challan...?
Also GSTR 3B late fee automatically calculated not available from starting of GSTR 3B return. Taxpayers and Consultants calculated himself...
If You are late filed Your GSTR 1 return then You ll pay late fee as per Your no of days later. It will help at the time of finalize or Annual return or Audit...!!!