Advance Receipt - Builder

Nandkishore (Student CA final) (48 Points)

30 May 2018  
one of my relative is Building Developer. and he received money from their customer in advance but he did not paid any gst on advance receipt and not disclosed in GSTR 1 any information regarding advance receipt.
Is it necessary to give information of advance receipt in GSTR 1. and pay tax on advance receipt.
Is there any consequences of non compliance.
kindly suggest me.
Thanks .