There are two options depending on the bank transfer entry status.

Delete the other side and re-enter the bank transfer

1. Delete the other side of the bank transfer in Cash Management.
2. Re-enter the bank transfer, if needed.

Re-enter only the missing side of the bank transfer

1. Determine the Bank Transfer Clearing account used for the deleted bank transfer.
    TIP: The Bank Transfer Clearing account is set in CM Settings, Bank Transfers tab.
2. Enter the missing bank transfer entry in Tasks and Edit Register. Use the Bank Transfer Clearing account as the offsetting GL debit or credit account. 

How do I enter a deposit, withdrawal, adjustment, service charge, or other transaction types to a bank account in Cash Management?
How do I delete, void, or remove a transaction in Cash Management?
How do I enter a bank transfer in Cash Management?