Amendment bill 2018-19 b 2b to b2c

One bill b2b outward supply invoice date 31.12.2018 which bill amount wrongly entered b2c invoice in gstr1 in the month of December 2018.
My query is this bill can amend in this year 2019-20 financial year.
Amendment gstr1 in September may possible because that period Dec 2018 gstr3b have already made.