GST RETURN

A person is manufacturing unbranded channachur (namkeen) and selling it for which rate of GST is 5 percent ,but for the A.Y 17-18 he has raised all invoice on which rate of GST charged is at 12 percent and filled GSTR -3b & GSTR-1 on that basis.For A.Y 18-19 can he raise invoice at 5 percent and file GSTR-3B & GSTR-1 accordingly ?