Do one of the following:
Set or clear a reminder for a specific task
If you set a reminder but don't set a reminder time, the default reminder time is used. To set the default reminder time, on the Tools menu, click Options. In the Reminder time box, select a time.
Set or clear reminders for all new tasks with due dates
Note If you assign a task with a reminder to someone else, Microsoft Outlook switches the reminder off so the person who accepts the task can set a reminder.