10 October 2018
Sir, I have submitted GSTR 1 but not filled for the period July 2018 to Sep 2018 as Quarterly returns, but by mistake I have entered the data only for the month of Sep.2018 but not for entire quarter and how to update july & aug. PLEASE KINDLY ADVISE.
11 October 2018
Once Submitted then no way for changes or corrections or editing...
But,
You can show the missed invoice details in Your next GSTR 1 return...