Once you've started creating reminders, you'll also start marking them as complete once you've finished with a task. If there's ever a time that you've created a reminder for a task that you later don't need to perform, you could always mark it as complete to get rid of it, but there's actually a better solution. The Reminders app also gives you the option to delete it.
- Launch the Reminders app from the Home screen of your iPhone or iPad.
- Find the task that you need to completely delete.
- Swipe left or right on the task or item name.
- You'll now see a delete button appear to the right of the task name.
- Tap on Delete to remove it from the list completely.
- The task will now be deleted instead of moved to the completed section as if you were to mark it as complete to get rid of it.