How can I tell who used an access code and who purchased a ticket?


Within a user's profile, you can see the Method of access to the entitlement. This will display if the user purchased the entitlement or if they used an access code. 

You can also export two lists: Users with Entitlement and Users who Purchased Entitlement.  You can then remove the duplicates from the list, which will show you the users who gained access from a method other than purchasing (most likely an access code).