GSTR 1

when you file your next uplcoming gstr 1 go to column. 10 amend B2CS and less this amount there and add this invoice in B2B that month return ( do not change origional invoice take )

ex- if you did wrong in oct go to your next upcomoing gstr 1 which one have to file and amend B2CS by column 10 less this value of invoice and add thjs invouce in your B2B with original invoice date