A national identification number is a unique number assigned by a government to its citizens, permanent residents, and temporary residents for the purposes of tracking them, work, taxation, government benefits, health care, and other governmentally-related functions. The number appears on an identity document issued by a country, such as an ID card, passport, or resident permit. The ways in which such a system is implemented are dependent on the country, but in most cases, a citizen is issued an identification number at birth or when they reach a legal age. Non-citizens may also be issued such numbers when they enter the country or when granted a temporary or permanent residence permit.
The length of the number, its specific purpose, and the term used to refer to it might vary depending on the country. For example, in Nigeria, the national identification number (NIN) is a set of eleven digits assigned to Nigerians of all ages and legal residents by the government. In Taiwan, a valid national identification number consists of one letter and nine digits, in the format A########C, where the letter records the cardholders first location of household registration, the first digit depends on gender, and the last digit is a checksum.
It is important to note that not all countries have a national identification number system. For example, Hungary does not have a national identification number, and the Constitutional Court decided in 1991 that a general, uniform personal identification code distributed to every citizen and resident of the country based on an identical principle is unconstitutional.
