By default, Project calculates the work required to complete a task by using the standard rate of each assigned resource. Project does not calculate the cost of additional work hours by using the overtime rates that you entered until you specify those hours as overtime work. For example, if a resource is scheduled to work eight hours a day and he or she enters ten hours of actual work, the two hours of additional time isn't automatically considered overtime work.
Choose View > Task Usage.
Choose View > Tables > Work.
Right-click the Work field and choose Insert Column.
(In Project 2007, select the Work field, and then chose Column on the Insert menu.)
In the Field name list, choose Overtime Work.
In the Overtime Work field, select the resource assignment for which you want to enter overtime work.
Press TAB to move to the field if it is not visible.
If resource assignments are hidden, click the task's outline symbol to display them.
In the Overtime Work field, enter the amount of overtime work for the resource assignment.
Note: The amount of overtime work that you specify is not added to the amount of work for the task because work always represents the total amount of work. Overtime work merely represents the portion of the total amount of work that should be considered and rated as overtime. When you enter overtime work, the duration of the task may be shortened, unless the task is a fixed-duration task type.