If you wish to join a golf club you will need to provide your membership number (previously named CDH) to your new club so that they can transfer your playing history and Handicap Index®. Your new club will then request your details.
If you ever change affiliated clubs, the previous club will follow the same process of resigning you as a member of their club and your new club will reinstate you as a member.
Your record will always remain attached to your unique membership number. No club should provide you with a new membership number.