You may have posted transactions to the correct period in PL but showing up with wrong period in NL. E.g. post the transaction to C5 in PL, but posted to L5 in NL.
This could happen if the user was posting transaction during period end process.
We cannot reverse this entry and user has only 2 options in this regard:
To leave the transaction as it is.
To delete the transaction from the system and then re-input the transaction correctly. If customer is taking this 2nd option, then they will need to look at the impact of the error posting as it affects their year-end figures, cost on the balance sheet etc. before deleting transaction from the system.