Flag important project events with milestones

By Bonnie Biafore

In the days of yore, a milestone was literally a stone that marked a point — a mile from the last stone, to be exact. For project managers and project team members, milestones mark points in a project, but project milestones don't measure distance. Instead, they highlight important events, such as the completion of a phase, a delivery of materials, or a payment for work performed.

The familiar diamond shape of milestones in a Microsoft Office Project 2003 schedule makes events easy to spot, as illustrated in the following figure. You can use milestones to draw attention to significant events without worrying about delaying a project. Because milestones in Project are tasks that have zero duration, finish dates don't change regardless of how many milestones you use.

Milestone tasks

Callout 1 Decision
Callout 2 Progress
Callout 3 Event

Types of milestones

The last task in almost every project schedule is a milestone because that keeps the finish date in the limelight. However, milestones work equally well for many types of events. The following sections describe several uses for milestones.


Moving forward on a project often depends on a decision of some kind. Many companies commit to projects for one phase at a time, and they decide to proceed to the next phase only if the results from the previous phase are acceptable. A milestone is the perfect way to delineate these crucial points in a project. As shown in the preceding figure, a decision milestone can act as the gatekeeper for action on a project.

  • Go/No Go     For many projects, particularly those with high risk and significant cost, the results of a feasibility study or the estimates from the planning phase might determine whether a project receives funding to continue or is canceled. The tasks leading up to a decision are linked to a Go/No Go milestone. If the project is canceled, that milestone represents the end of the project. Otherwise, tasks scheduled after that milestone begin.
  • Project start     Starting a project with a milestone makes it easy to reschedule the entire project should the kickoff date change. For example, if the board of directors doesn't approve a project during its May meeting, you can change the date of the project start milestone to the date of the August meeting so that the entire project is delayed.
  • Choice     Some choices affect a project so significantly that work can't continue until a decision is made. For example, construction on a house can't begin until the homeowner chooses the builder.

Some decisions affect all the work that follows. For example, if you decide to build a house out of brick instead of wood, some of the construction tasks and resources will change. In this situation, the project manager must modify the project plan after the decision is reached.

An approval is a special case of a decision milestone. Often, additional work can't begin until previous work has been approved, such as when a county building inspector must approve the electrical wiring before the drywall crew starts closing in walls. And in a Go/No Go decision, a Go decision is approval to continue.

Approvals can also act like a project start milestone. If the project plan isn't approved the first time around, the Approved Project Plan milestone is delayed until the plan is acceptable to the project stakeholders.


The true progress of a project lies within its work packages, but completed milestones provide a quick picture of overall progress. This is a benefit when adding milestones to flag progress during the execution of a project instead of just at the end of the project.

  • Interim progress     Keeping a project on schedule is much easier if you have checkpoints throughout the project. If you reach an interim milestone only to find that you're behind schedule, you can take corrective action while there's still time to recover. For example, if you're building the Great Wall of China, you could create milestones for every mile of the wall so that the project manager who takes over when you retire isn't faced with a 10-year schedule overrun.
  • Project finish     The end of a project is a common place for a milestone because the end date is often crucial to the success of the project. For example, an updated version of accounting software that reflects the 2005 tax law changes won't sell very well if its release date is May 1, 2006. The "Deadlines" section, which follows, explains how to flag hard deadlines in a project.

Milestones are also handy when one team hands off control to another team. Handoffs often occur at existing project milestones, such as the end of a phase. If a handoff occurs at another time, a milestone can keep the new owners apprised of their pending responsibility.


Many projects have external dependencies, which are just as important as the work done by the project team. If you don't manage the progress of work, but you expect deliveries on a specific date, milestones are the answer. For example, on a commercial construction project, you probably wouldn't manage the fabrication of the structural steel — but you want it to arrive by the time that construction begins.

You can use milestones for any kind of external dependency. Deliveries of raw materials, preassembled components, equipment, or custom software are perfect points for milestones.


You can even use milestones to show brief events that occur during a project. For example, if you hold a team-appreciation ice-cream social once each quarter, you can add a milestone on that date. See the "Soft vs. hard: Deadlines and date constraints" section, which follows, to learn how to tie an event to a fixed date.


Deadlines are target dates that arise for many reasons. For example, tax returns are due on April 15th, and clients sometimes include a completion date as a contract term. Some deadlines are harder than others, however. For example, if you can't finish your tax return by April 15th, you can file for an extension with the Internal Revenue Service. But, if your company's contract comes with a penalty for late delivery, you must do everything you can to keep the project on schedule. The next section describes features in Project for flagging milestones with soft and hard deadlines.

Soft vs. hard: Deadlines and date constraints

Depending on the significance or consequences of a milestone's date, you can use deadlines or date constraints to manage critical dates.

Hard date constraints, such as Must Finish On, decrease the flexibility of a project schedule by limiting when tasks can occur. Because of this, Project might not be able to recalculate a schedule in response to changes that you make.

In contrast, the Project deadline feature highlights missed deadlines without constraining the schedule. Project schedules tasks that have deadlines like any other tasks. However, if a task finishes after its deadline date, Project displays a task indicator in an indicators field, as shown in the following figure, to warn you of the missed deadline.

A task has missed its deadline date

To add a deadline to a task, do the following:

  1. Double-click the task.
  2. In the Task Information dialog box, click the Advanced tab.
  3. In the Deadline text box, type the deadline date or click the drop-down arrow to display a calendar on which you can click the date.

Date constraints can also wreak havoc with task dependencies. When a task is delayed past the date constraint for its successor task, Project must choose between honoring the date constraint or keeping the dependency between the two tasks. By default, Project honors the date constraint and disregards the task dependencies. You can identify disregarded task dependencies by inspecting the schedule for link lines that wrap more than they should, as illustrated in the following figure.

Missed date constraints in Project

Callout 1 Missed Constraint Indicator
Callout 2 Task dependency not honored

If you create a milestone that has a hard date constraint, such as an end date that comes with a costly late-delivery penalty, set Project to honor task dependencies instead of date constraints. Project then displays a constraint indicator to warn you of the crucial missed date.

To honor task dependencies rather than date constraints, do the following:

  1. On the Tools menu, click Options, and then click the Schedule tab.
  2. Clear the Tasks will always honor their constraint dates check box.
  3. To honor task dependencies in the active project and in all new projects, click Set as Default.


Milestones highlight significant project events, such as decisions to proceed; completion of phases or major tasks; delivery of project results; meetings; progress payments; and deadlines, such as ones for submitting a proposal. Because milestones in Project have zero duration, you can use them to emphasize key events without worrying about extending the duration of a project. Milestone deadlines can be soft or hard. Although Project provides for both types of deadlines, project schedules are most useful when you limit hard date constraints in favor of deadlines.

About the author     Bonnie Biafore is a PMI (Project Management Institute)-certified Project Management Professional (PMP). She is a consultant, trainer, speaker, and award-winning author of several books about investing, personal finance, and project management, including On Time! On Track! On Target! Managing Your Projects Successfully with Microsoft® Project (Microsoft Press, 2006).

Applies to:
Project 2003