Shoudl gstr3b for filed - registration on september 2017 ?

Hi Friends,

One of my friend took a GST registration on September 20th 2017. He registered as a voluntary taxpayer. Is it necessary for him to file GSTR 3b and other returns from July 2017 & August 2017 as well ?  or Is it enough if he starts filing from the month of September 2017 as the first month ?  Please guide me.

Will there be any late fee applicable ?

Thanks,

Aravind.K