In V 4.0 of the MSF templates there is a StartDate and and FinishDate that are by default mapped to the task start and finish date in Microsoft Project (if you are using a project file). Thus you can use the finish date as the deadline date...
Or if you wish to have the finishdate be updated from some sort of state transition or manually then you could create a seperate custom field for DeadlineDate. This would give you the advantage of seeing not only what is currently overdue via something such as
today > DeadlineDate
but also historically what was late on delivery. e.g
Show work items where FinishDate > DeadlineDate.