When to use subtasks? - Actonic – Unfolding your potential
Become an Atlassian Knowledge Champion

When to use subtasks?

A subtask can be created and used for the issue for either splitting the issue into smaller parts or for allowing several aspects of the issue for assigning to different people. Subtasks are best used in instances in which a project moves at different levels.

Subtasks are also best used when you wish to communicate better while providing full transparency. It turns out to be more effective in date and cost estimation.