how to reduce balance in GSTR1 (exampted sales)

sunilkumar k s (71 Points)

22 November 2018  
instead of filling monthly gstr1 just filed quarterly how to rectify
ex,: april-25000
may-25000 and
june-25000 b2c sales we rquire to file monthly but filed quarterly June 75000 how to rectify (April to Jun 2018) and continue monthly return