Set a task reminder
You can set a reminder for a task in Tasklist. You can also set a reminder for a task in Microsoft To Do. If you have a To Do task linked to a Tasklist task, Tasklist automatically updates the linked To Do task with changes you make to the Tasklist task, including setting a reminder. As a result, you may get the same reminder from both Tasklist and Microsoft To Do. Tasklist will send you a reminder only if it is running at the time you set for the reminder.
You can set a reminder for a task by clicking on Edit task in the Task tab of the ribbon. Check the checkbox to activate the reminder, and use the drop-down calendar to set the date for the reminder. The reminder time defaults to 9:00 am, but you can set a different time.

Tasklist will send you a Windows "toast" reminder at the time you set, but only if Tasklist is running at the time. Tasklist does not give late reminders. (A "toast" reminder is one that pops out of the bottom right corner of your screen.)