If the Time Entries on a Phase can be discarded, a Phase may be permanently deleted.
Click Show X Archived, if the archived Phases are hidden.
Click the three-dot menu of an archived Phase and select Delete.
In this case, all the Time Entries and Work Plans on this Phase will be permanently deleted. Click the Permanently Delete button.
The Phase will be permanently deleted along with all Timesheets and Work Plans.
Deleted Phases cannot be restored.