A method, apparatus and program storage device for providing real-time file system charge-back accounting with real time historical minimum and maximum usage per user or group during a report cycle. In a first storage area of file system memory, space allocation data for a current accounting period is monitored and persistently maintained. A minimum, maximum and average space allocation is calculated for the management object during the current accounting period. The calculated minimum, maximum and average space allocation for the management object may be moved to a second storage area of the file system memory while beginning to monitor and persistently maintain space allocation data of the management object in the first storage area of the file system memory during a subsequent accounting period.