Only allow promo one time

We offer an inexpensive trial to our main product often, but want to make it so that people can only use that promo one time, or maybe once a year. If they kept doing the promotion, we’d like it to say they can’t because they already used their promo.

Is there a way to do this? I banged my head into it and can’t figure it out.

thanks

Well, trials are tricky in that regard, since people can just register over and over again with different email accounts until they get bored.

You could implement a tracking using browser/flash cookies, but those can still be deleted by the user and you wouldn’t be able to tell if it’s their first try.

If you only show the offer to those logged in, then you could track its user in their account adding a row to the usermeta table, but that doesn’t stop the person from creating a new account and doing it again.