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How to Sort Tasks by Start Date Within Summary Groups in Microsoft Project

Maira Mehtab Sep 28, 2026 869 views

Question details

The user wants to sort project tasks chronologically by their start dates within specific summary headings without altering the predefined order of those summary headings.

How to Sort Tasks by Start Date Within Summary Groups in Microsoft Project

Product: Microsoft Project
Device & OS: not provided
Scenario: Organizing a project schedule where tasks need to be ordered by date within multiple fixed phases or summary groups.
Observed behavior: When applying a standard start date sort, the software reorganizes the entire schedule, moving summary headings out of their desired order based on the earliest start dates of their sub-tasks.

Before you start

Ensure you have clearly defined the correct sequential order of your summary groups before proceeding, as we will lock these in place using a custom field.

Solution 1Recommended

Use a Custom Number Field to Preserve Heading Order

By assigning a sequential value to each summary heading using a custom field, you can force the software to preserve your group order while correctly sorting the individual sub-tasks by date.

A standard sort evaluates the earliest start date inside a summary group and will move the entire group if a sub-task starts earlier than one in a preceding group. Anchoring the headings with a custom Number field bypasses this behavior.

Insert the Number1 column

Right-click on any column header in your Gantt Chart view, select 'Insert Column', and choose 'Number1' from the dropdown list.

Number your summary groups

In the newly added Number1 column, type '1' for your first summary heading, '2' for the second, and continue sequentially. Leave the fields for all detail sub-tasks empty or set to zero.

Open the Sort dialog box

Navigate to the 'View' tab on the top ribbon, click on 'Sort' located in the Data group, and select 'Sort By...' to open the advanced sorting options.

Configure the primary and secondary sort criteria

In the Sort dialog, set the 'Sort by' dropdown to 'Number1' and select Ascending. Next, set the 'Then by' dropdown to 'Start' and select Ascending.

Apply sorting while keeping the outline

Make sure the 'Keep outline structure' checkbox at the bottom of the dialog box is checked, then click 'Sort' to execute.

Use a Custom Number Field to Preserve Heading Order

Outline Preserved Successfully: Your detail tasks are now chronologically sorted within each phase, while your overarching summary headings remain exactly in the custom numbered order you assigned.

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Frequently Asked Questions

Why do my summary tasks move when I sort by Start Date?

When you sort by Start Date, Microsoft Project looks at the earliest start date of any sub-task within a summary group. If a sub-task in your third group starts earlier than the tasks in your second group, the software will shift the entire third group above the second one.

What does the 'Keep outline structure' option do?

The 'Keep outline structure' checkbox ensures that detail tasks remain nested under their original summary tasks during a sort. If this is left unchecked, tasks will be mixed together chronologically across the entire project, effectively breaking your project phases.

Can I return to my original task order after making a mistake?

Yes. If you need to revert to the exact order in which you initially entered the tasks, navigate to View > Sort > Sort By, and choose to sort by the 'ID' column in ascending order. This will restore the default entry sequence.

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