GSTR 9 n 9C for FY 17-18

on 1/4/17 proprietorship firm converted into partnership firm and during transition period tax consultant has taken gst number in proprietorship PAN. Till Nov 2017 gst sales were filed in proprietorship firm's gstn and from Dec 17 onwards in partnership firm. however in income tax total sales were reflected in firm only. GSTR 9 of proprietorship firm was not filed and only partnership firm was filed in which total sales of 17-18 were disclosed. Now the dept has issued notice for non filling of GSTR 9 of proprietorship firm. sales in proprietorship in gstn was 2.06 cr.

whether the plea sustain that we have disclosed total sales in partnership firm gstr 9 and if not what consequences to be born.