If a template has never been used, it can be deleted from the system. Once it has been used, it cannot be deleted, but instead should be archived. Archiving the template will remove it from the Audit Templates list and will mean it can no longer be scheduled. 

From the Admin dashboard, select Audit Templates

To the right hand side of the template you wish to delete/archive, select Actions

To delete the template, select Delete

To archive a template, select Edit

You are now taken to the edit screen.  Near the bottom of the screen is the option to mark the template as Archived. Check this box and click Create.

The audit template will now be hidden from the list, but can be retrieved at any point by selecting the Show archived templates button