Hello,
Sorry...my co-worker just reminded me your question is about cost. I'll keep my part below...since labor costs are associated with hours. Make sure people realize actual hours will not be removed by simply deleting a task. We don't do costs, but I'll look into it here today...for we use OWB, and see if cost sticks around too.
Original response....
The situation you mention happens in MSP, Open Workbench & Clarity. You cannot delete a task that has Actual hours posted to it.
When you 'delete' a task with Actual hrs, it will remove any remaining ETCs and move the task to the bottom of the WBS under a new phase called Deleted Tasks. It will always keep all actual hrs posted.
The tool is working correctly. We don't want time 'disappearing'. Effort was applied to that task...it needs to stay.
If you want to totally delete the task, the person who entered the Actual hours can go back to that time period's timesheet, remove the hours from the task you want to delete AND re-enter that time to another task in the project.
Hope this helps.
Lisa