All persons born in metropolitan France and the overseas departments (DOM) are registered on the national directory for the identification of natural persons (RNIPP). Persons registered in this directory are assigned a registration number, which is used most notably by medical insurance authorities for the issuance of the "carte vitale". This identification number is unique to the individual and is composed of 13 figures denoting: sex (1 digit), year of birth (2 digits), month of birth (2 digits) and place of birth (5 digits). The next 3 digits represent the chronological order number, which allows for a distinction between people born in the same place within the same period. The national registration number is completed by a 2-digit control key.
This registration number is popularly known as the "social security number".