Sales missed in Dec-17 month 3B

vinay joshi (83 Points)

17 August 2018  
Hi all,
we have missed taxable sales amount in Dec 17 month 3B but we declared these sales in Dec 17 month GSTR 1. Now my question is can we declare the missed sales in July 18 month 3B? If I do so then there is mismatch in sales of this FY 2018-19.
please tell me how to correct the mistake.

Thanks in advance