# Linked Tasks Can Be Flexible or Inflexible

Constraints applied to linked tasks can be flexible or inflexible. A flexible constraint allows a task’s start and finish dates to be automatically recalculated when the dates of other tasks in the same linked sequence change. Examples of flexible constraints are the As Soon As Possible constraint and the Start No Earlier Than constraint (which allows a task to start later only if you schedule your project from the project start date and not the project finish date).

Inflexible constraints tie a task to a specific date. Typically, the dates for a task with an inflexible constraint don’t change when the dates of other tasks in the same linked sequence change. These dates remain fixed. Examples of inflexible constraints are the Must Start On and Must Finish On constraints.

Constrain a task if:

- The constraint reflects an actual time restriction in the real world.
- The project will be penalized for not starting or finishing by a specific date.

If a task doesn’t absolutely need to start or finish on or near a specific date, don’t apply an inflexible constraint. When you apply inflexible constraints to tasks, you bypass the advantage of allowing Microsoft Project to calculate task start and finish dates for you automatically as the schedule changes. If a constraint is unnecessary, change it.

Keep in mind that constraints may become undesirable when you reschedule tasks. For example, if you specify that a task must start on a specific date, but its predecessors actually take longer than planned, there might not be enough time for the predecessors to finish before the constrained task is scheduled to start. If a predecessor task ends up overlapping the constrained task, a resource assigned to both tasks might be overloaded with work on the overlapping days. On the other hand, if the predecessor tasks happen to start a week earlier than planned, you might end up with a week of dead time in your schedule.

©1996-1997 Microsoft Corporation. All rights reserved.