GST Return After Death of Assesse

gaurav bhootra (CA) (52 Points)

01 September 2018  
Sir one of my clients having proprietary firm died in February 2018 and the said fim now run by his son. They have made sale and purchase transaction using GST no. of his father and we have filled GST return of using that GST no till March and we have not surrendered that GST No. till now.
My question is that can we use GSTN No. of demised person for purchasing and selling goods.
Is there any provision under GST Act for Adding legal heirs?