
No amount of actual effort will complete the task since the system allows you to go over-budget by default. So what you need to do is either set "remaining effort" to 0, which completes the task, or set % completion to 100%. Either of those will let the task be completed. However, I have to say that I still prefer the time tracking system for this scenario so that you can see exactly when all of the time was reported. If users are just adjusting the actual effort field, you cannot pull a report saying "show me all time reported in November" as an example.