To monitor the charges accrued on the connection and also on the internal phones, the charges are recorded by the PBX for each subscriber separately. From time to time, the total charge may be reviewed on the corresponding phone and deleted, if necessary. The deletion has no influence on the call charges recorded in the call data memory of the PBX.

To check the charges during a call or directly afterwards, the charges are transmitted to ISDN phones unchanged at the moment they are accrued even if the receiver is on-hook.