Revise GSTR 1 for FY 2018-19

Madhu Sudhan (B.Com) (32 Points)

20 February 2021  
Hi,
My father's accountant had shown fake sales for three months in FY 2018-19 and no GSTR 3B filed. After that, he became unreachable. Now I want to close his GST and found this blunder.
Can I amend the fake sales he has shown by mentioning the invoice number and changing the amount to zero?