GST returns not filed since July 2017

Jayesh sandha (14 Points)

06 June 2018  
One of my relative have not filed any GST return since July 2017
He has also issued invoice to his clients and also taken invoice from different parties (suppliers). I want to know how much penalty he has to pay and at what rate of interest if he has any liability in each month from July 2017. Is there any maximum limit for penalty for non filing of returns?