Dear Sir,
30.04.2018 is the last date for GSTR filing. For ITR last date is 31.07.2018. If you have obtained GST registration then you need to file NIL GST return monthly otherwise not required.
LLP is compulsorily required to file ITR irrespective of turnover. If not filed within due date you may end up in paying late fee and assessment by deptt.
Thanks