Sales return treatment in gst

ankush soni (student) (100 Points)

05 June 2020  
dear experts ,
pls guide us about the necessary steps to be taken when a b to b sale is cancelled after filing of gstr1 as well as the gstr 3b of relevant months by both level of dealers in below mentioned two conditions
1. where the payment of bill is due.
2. when the payment of bill has been made.
pls guide with your valuable and expertise opinions.