You would use this procedure to make corrections to the bank balance.
Go to GRN>Bank Account>Bank BNK > Bank Account > Bank Maintenance
Enter your bank code and hit ok
Confirm information is correct.
Hit Add New Transaction
Enter the location code, type code, and ledger date for your correction.
It will auto fill the next receipt number, hit ok
You can either enter it as reconciled now and add the reconcile date or you can put it in as active to reconcile at a later date.
Enter a Decription Description that makes sense to you and you will understand later on if asked about it.
Enter the amount and source code. Using a source code other than M creates the one sided transaction only affecting the bank balance.
Hit ok and your transaction in the bank is complete.