Gstr 3b filing for august

I have a query that If one GSTN No. is comes on 15-aug-2017 then when his liability of Gst arrisses.....and one more query is that if he has the no. purchase bill in the month of aug 2017. can he issue the all of his sale bill of courier services in sep 2017.

 sir/ medam

our clint is registred  under gst act  can menditary for filing gst 3b returns

Mr.Varinder 

Yes Virinder there is a late fees but one loop hole

Thanks with regards

Yogesh Nain

9899979745