Resolution
To show the value as 100% in the task % Complete field when the resources complete work on their task assignments, complete the following steps:
1. Open any project in which the % Complete is not calculating automatically
2. Click Tools - Options and select the Calculation tab
3. Select the "Updating task status updates resource status" option
4. Click OK
From this point forward, Microsoft Project will automatically calculate the task % Complete based on the actuals submitted by team member on uncompleted tasks only. For those tasks completed prior to changing the Options setting above, project managers must manually set those tasks to 100% complete by double-clicking the completed task and entering 100% in the Percent complete field.
Best Practice: Enable this setting in every existing project and make sure that this is the default setting in every enterprise project template as well.