composition return

You have to file your GST return quarterly but as of now 

GSTR 3B has to be filed till the month of december (monthly)

and GSTR1,2,3 is to be filed quartely from 3Rd qtr of this Financial Year, i.e from 1/10/2017 and for july,aug,sept 2017 it is monthly.

As per the Press Release by GST Council on 22nd Meeting.
Taxpayers needs to file GSTR 3B on Monthly basis till December,2017

5. To facilitate the ease of payment and return filing for small and medium businesses with annual
aggregate turnover up to Rs. 1.5 crores, it has been decided that such taxpayers shall be required to file
quarterly returns in FORM GSTR-1,2 & 3 and pay taxes only on a quarterly basis, starting from the third
quarter of this financial year i.e. October-December, 2017. The registered buyers from such small
taxpayers would be eligible to avail ITC on a monthly basis. The due dates for filing the quarterly
returns for such taxpayers shall be announced in due course. Meanwhile, all taxpayers will be required to
file FORM GSTR-3B on a monthly basis till December, 2017. All taxpayers are also required to file
FORM GSTR-1, 2 & 3 for the months of July, August and September, 2017. Due dates for filing the
returns for the month of July, 2017 have already been announced. The due dates for the months of
August and September, 2017 will be announced in due course.