This question after GST has sudden emerged in so many users/consumers mind, although same was well described under Service Tax Act but many new questions raised due to merging of all Acts in one Act. I have tried to deal possible situations which may help you understand concept, kindly comment if any contrdict views are there because we all are learner and no one is EXPERT at this satge.
Govt has deferred dates for GSTR 1 & GSTR 2 for the month of July 2017, from 10th Aug & 15th Aug 2017 to 5th Sep & 10th Sept respectively but at the same time it has introduced for 2 months only a New Form GSTR 3B which needs to be filed on or before 20th Aug 17 for July 17 working. Therefore it is prerequisite to start efforts from today because from 24th July, 2017 window for upload of Invoices is being opened.