Todoist creates automatic reminders for tasks that have a due date or associated time. For example: if your task is due today @ 10am, Todoist will automatically send a reminder 30 minutes before this deadline.
Setting reminders manually
It's easy to manually set and manage reminders. To do this, simply:
Open a task's menu by clicking on the menu icon ().
Click Reminders menu item to open up a window where you can manage your task's reminders.