How Bank Balance is Updated?

Dear SAP Business ByDesign Experts,

I would like to ask, how bank balance is updated at the system? Is it via bank statement or via system transactions?

I am asking because we have created our payroll and letter of guarantee add-on. So, some of the outgoing transactions are conducted via petty cash or bank, but from the add-on screen and not from traditional bank or petty cash screens.

Thanks & Regards,

Amr