The posting period for manually entered Cashbook transactions, is governed by the parameter ‘Using Journal Date Resolve Period Byte’.
If the value is set to ‘0 – Customers / Suppliers Periods’ the transaction will post according to the Current Customers / Suppliers period, i.e. the bank charges would post according to the Suppliers period.
If the value is set to ‘1 – General Ledger Periods’, then the transactions will post to the GL Period current at the time of posting the entry to the GL.
Note that saving the manual Cashbook entry does not post it to the GL straight away. That is done either manually using the Post to GL button at the bottom of the Cashbook page, or when closing the page which will also post any unposted manual transactions to the GL as well.