Unique Citizen Reference Number or UCRN is a number assigned to persons in Scotland at birth, or when they use certain government services.
According to the National Entitlement Card’s Information Architecture document:
The UCRN is an opaque identifier (i.e. it has no semantic value of itself, containing no personal information) that is held in both myaccount and the CMS system for the purpose of data integrity. It is not held on the card. The UCRN is allocated by National Records of Scotland (NRS) as it forms part of the National Health Service Central Register (NHSCR). There are clear rules associated with the UCRN and how it can be used. These rules are covered in agreements between National Records of Scotland (NRS), the Improvement Service and Service Providers. The rules are designed to ensure that the UCRN is used in a controlled way in line with the Scottish Government’s Privacy Principles