The option to furnish the details of outward supplies will expire on the 13th of the following month. For e.g. Last date for furnishing details under IFF for the month of Jan will be 13th Feb. Note: As the date of generation of GSTR 2B is the 14th of the subsequent month In my opinion government needs to reconsider the date of GSTR 2B as the due date for furnishing GSTR 1 and details under IFF is the 13th.