Need more control over Registration for your WordPress site? If so, you better use groups of invitation codes and send invites to relevant users. You can track the number of users registered per each invitation code. Invitation Codes are generated automatically once you enter the group name. You can deactivate any existing group once you don't want the invitation code to be used any more The plug is also integrated with WishList Member and allow to assign WLM group level per each invitation code allowing any new registered user to accept WLM level.
CM Invitation Codes