The department has already issued a circular on 29th December 2017 for any rectification in GSTR-3B and GSTR-1, hence you can go through that circular which clearly explains the dos and the donts
July to March GSTR 1 sirf INOVICE no..wrong put ho gye hai..Kya m 2018-19 ki June return m un sbi billo ko amendment KR skta hu..
And Gst act k according law m
Please suggest me