# Add sub-tasks and dependencies

> Split work into sub-tasks, mark which tasks block others and tie tasks to milestones inside a project. How they show up and what they do not do.

Source: https://priortasks.com/docs/tasks/sub-tasks-and-dependencies/
Last updated: 2026-11-05

Sub-tasks, blockers and milestones link tasks to each other inside one project. They appear in the **Sub-tasks and dependencies** section of a task that belongs to a project. A task outside a project does not have them: use a [checklist](https://priortasks.com/docs/tasks/checklists/) there.

## Add a sub-task

1. Open a task that is in a project, in the full edit sheet. The **Sub-tasks and dependencies** section is at the bottom. On a new task, add it from the **+** menu to set a parent or blockers before you save. Creating sub-tasks needs a task that already exists.
2. Type a title under **New sub-task** and choose **Add**, or press <kbd>Enter</kbd>.
3. Open the new sub-task from the list to give it a date, a priority or a checklist.

A sub-task is a normal task. It lives in the same project and area as its parent, keeps the parent's milestone, and starts as **Todo**, or **Backlog** in a software project. The heading shows how many are done, like "Sub-tasks · 1/3".

To turn an existing task into a sub-task, open it and pick a **Parent task**. The list offers the open tasks of the same project. A task cannot be placed under itself or under one of its own sub-tasks. Choose **No parent** to detach it.

## Mark a task as blocked

Under **Blocked by**, choose **Add a blocking task** and pick a task from the same project. Remove one with its **×**.

- A blocker that is not done shows a lock. A done blocker shows a check.
- While any blocker is open, the task shows a **Blocked** badge on its project board card.
- Blocking is a signal, not a lock. You can still complete a blocked task.

## Add a milestone

When the project has milestones, a **Milestone** menu lets you attach the task to one. See [Milestones](https://priortasks.com/docs/projects/milestones/).

## How they behave

- Sub-tasks appear in your lists, on Today and on boards like any other task. Completing a parent does not complete its sub-tasks, and the other way round.
- With [automatic time blocking](https://priortasks.com/docs/planning/time-blocking/), a Pro feature, the planner places a sub-task and leaves out a parent that still has open sub-tasks. It also schedules a blocker before the tasks it blocks, and starts those after the blocker's last block.
- Moving a task to another project clears its parent, milestone and blockers, because they only make sense inside one project.
- In a shared project, anyone who can edit the project can link tasks. A viewer cannot.

## Good to know

- Sub-tasks count as tasks for XP in Game mode. Checklist items do not.
- Prior AI can propose sub-tasks when a Scrum story is too big. See [Split a story](https://priortasks.com/docs/agile/split-a-story/).
- Assistants connected through [MCP](https://priortasks.com/docs/integrations/mcp/) can set a parent and blockers too.