When should I create a subtask ?

[Baijia Chen]

Hi everyone, our team is applying Epic -> Story/Task -> Subtask workflow

Recently I got requirements from our Program Team to create the sub-task (even just a blank sub-task) for each story even the story is a small story point ticket (i.e. a UI bug fix). They said it is a good way for task tracking?

Based on my understanding, the sub-task usually is applied to a complex task (high story points) or a task that needs to be worked on by multi teammates.

It makes me confused about the definition of the sub-task function. 

[Jack Brickey · Accepted solution]

I don’t believe there are any rules. Personally I only create sub tasks if I feel the task story isn’t clear or the sub tasks will be done by different folks. Another example might be: document the story, implement the story, test the story. Keep in mind that if using scrum/sprints the story should be completed within a single sprint, otherwise the story should be broken into multiple stories not sub-tasks. 

[Matthew Tsugawa]

If your team uses Story Points and not Time Estimates (and of course enabling Time Tracking) then you should push back on creating Sub-tasks as a common practice. There are at least a couple of unsupported cases where Sub-tasks will not work as you'd expect with your time estimation efforts. Notably with Epics but also with the Sub-task itself having no relation to the estimation value of the "parent" Story/Task. I won't get into the details but it is explained through many links in this post which you should read all of the Accepted Answers. https://community.atlassian.com/t5/Jira-questions/Summarizing-story-points-from-sub-tasks-in-parent-task/qaq-p/1031210

In the end the teams I've worked with simply decided not to use Sub-tasks as they are not implemented the same way as Stories or Tasks when it comes to using Story Points. It is easy to remove the Sub-task as an Issue Type to avoid having to explain this subtlety to current and future Project Managers who want to estimate time in JIRA.