The system checks the journeys entered each day to determine if the first and last journey started/ended at the employee's base to calculate what commuter adjustment is applicable.  For night workers because their shift starts on one day and ends on the following day the system applies the commuter adjustment because it isn't seeing that the return to base or starting from base is occurring on the same day.

What we advise is that all journeys relating to the night shift uses the start of shift date.  That way the system will see that the first and last journeys have started/ended at the employee's base on the same day.