TO BE ABLE TO MARK 100 PHYSICAL PERCENT COMPLETE WHEN AN ACTVITY HAS BEEN COMPLETED

The physical percent complete reflects the actual progress made on the activity's work products so far. Physical percent complete can be manually entered by people familiar with the status of the activity's work products or it can be based on the completion of assigned Steps. Always in the range 0 to 100.

However once an activity has been completed by putting in the Actual finish date you cannot change the physical works complete to be 100 %.

This occurs when the Activity Percent box has been ticked, in the project settings, calculations tab at the start has been ticked, and cannot be changed later.