I've had a similar thing when renting from National. The codes from the company I used to work for "persist" automatically when I make reservations. I could probably make an effort to remove the code, but I've never made the extra effort and always wondered what would happen if something happened. I would argue that National should have a responsibility to re-validate the codes periodically but the never have. Not sure how that would fly in court but certainly that can't shirk all responsibility here.