Using the information from the updated resource schedule (i.e. working time of labour resources, usage time of equipment, quantities of materials) and the actual cost rates, as well as the information from the approved expense forms, the Project Manager tracks the actual costs that occurred during the reporting period against the tasks and updates the Cost Schedule accordingly. It is recommended that the Cost Schedule is updated on a regular basis and if possible with the same frequency as the Activities Schedule (i.e. using the same status date). Frequent updates to the Cost Schedule not only save time in the long run, but they also allow the Project Manager to quickly identify potential cost problems. Small variances from the planned cost that may seem unimportant, they might cause significant problems in project’s progress or even a budget overrun if corrective actions are not undertaken promptly.
In case that you are using specialised software for tracking project’s progress, the updated Cost Schedule will be prepared automatically by the program, using the information of the updated activities and resource schedules (refer to 7.4.3.2). The only thing that you have to do in this case is to check whether your initial estimates for the cost rates and the costs per-use are still valid or you have to use updated values. Obviously, the approved travel, administrative or other incidental expenses that incurred during the reporting period, have to be entered manually in the Cost Schedule. It should be mentioned that each time the activities and resource schedules are updated, the program apart from updating the actual costs; it updates also the remaining costs (i.e. the estimated costs that are expected to be incurred for a task, resource or assignment).
In case that you are not using specialised software for tracking project’s progress, the above actions should be performed manually, using the information from your updated schedules and probably an excel spreadsheet to speed up the calculations.
When updating the Cost Schedule is very important to create a new copy of the schedule and maintain an archive of each version. In this way, you will never lose the history of the project and you will also have a copy of every schedule for audit purposes.
After updating the schedule, do not forget to notify the appropriate stakeholders for any modification to the cost information that was judged as necessary and affects their assignments. Besides, be aware that Cost Schedule updates may require adjustments to other aspects of the project plan, such as Activities and Resource Schedules.
In special cases, cost schedule updates may result to changes to the approved cost baseline (budget updates). These changes may come up in response to scope changes. If you find that actual costs are so different from the baseline estimates and thus any comparison between the two is meaningless, rebaselining (i.e. save a new baseline for the Cost Schedule) may be needed to provide realistic data for measuring cost performance. However, care must be taken before rebaselining, because historical data will be lost. It is recommended that rebaselining should only be used as a last resort in controlling costs. Instead new cost performance targets should be the normal outcome of schedule update.