Summary Tasks, Subtasks, and Outlines

An outline gives a Project plan structure. A task indented beneath a higher-level task becomes its subtask, and the higher-level task becomes its summary task. Summary tasks can represent phases or other high-level portions of work, while subtasks describe the detailed work inside them. For a new plan’s first setup steps, see Creating a Project in Microsoft Project.

Build the outline

In the desktop Gantt Chart view, select the task that should become a subtask and choose Task > Indent. Project makes the task a subtask of the task above it and treats that task as the summary task. Choose Outdent to move the task back to the level of the task above it.

There are two useful planning directions:

Top-down: create major phases first, then break each phase into detailed tasks.
Bottom-up: list the detailed tasks first, then group them into phases.

Outlining changes hierarchy, not schedule relationships. A summary task and its subtasks do not automatically create predecessor or successor links. Add dependencies separately after the outline is organized.

What rolls up to a summary task

With automatic scheduling, a summary task’s schedule span is driven by its subtasks: it starts at the earliest subtask start and ends at the latest subtask finish. The summary bar therefore gives a phase-level view of the work beneath it.

Rollups are not simple addition for every field. Cost and work values total the subtask values, while duration and baseline values do not always behave as simple sums. Treat a summary value as a calculated view of the underlying tasks, not as an independent estimate that automatically rewrites every subtask.

You can still change a summary-task duration directly, but doing so does not necessarily change the durations of its subtasks. If the summary task’s dates or duration are intended to describe detailed work, check the subtasks and scheduling mode after making the change.

Assign resources to subtasks rather than summary tasks, because assigning at the summary level can make overallocations harder to resolve.¹

Show or hide the outline

Desktop Project can show all subtasks, show subtasks only through a chosen outline level, or expand and collapse one summary task. Use the Outline controls in the View tab for plan-wide visibility, or the expand/collapse control beside an individual summary task. In Project Plan 365, find outline options under Project.

The project summary task

The project summary task is a special top row representing the rollup of the entire project. It is different from a summary task that you create for a phase. In desktop Project, show or hide it from Format > Show/Hide > Project Summary Task. The project summary task must be shown when budget resources are applied to a project.¹

The project summary task is useful when you need one row for the project’s overall span or need to inspect project-level rollups. It does not replace a meaningful phase outline.

Why Indent or Outdent may be unavailable

Common causes include:²

A first-level task cannot be outdented farther; indent the tasks that should belong to a first-level summary instead.
Tasks belonging to a subproject in a consolidated master project cannot be outdented beyond that subproject’s level.
Assignments shown in Task Usage or Resource Usage are not tasks and cannot be indented or outdented.
The outline controls work only in supported task views, including Gantt Chart, Task Sheet, and Task Usage.
Sorting without retaining outline structure or grouping tasks can disable ordinary outlining controls.