I have to file GSTR-3-B for the month of Sept 2020 due date of which is 22-10-20. With effect from Jan 2020 till today there is some left out ITC also which has not been taken till today in any 3-B . As I have to take the left out ITC, I would like to know as from which month the left out ITC can be taken into 3-b for the month of September 2020.