Keywords: national identification number, identity card number, track, credit, birth date, residential registration, marriage divorce registration
 

A national identification number or National Identity Card number is used by the governments of many countries as a means of tracking their citizens, permanent residents, and temporary residents for the purposes of work, taxation, government benefits, health care, and other governmentally-related functions. Sometimes, the number will appear on an identity card issued by a country.

The ways in which such a system is implemented is dependent on the country, but in most cases, a citizen is issued a number at birth or when they reach a legal age (typically the age of 18). Non-citizens are issued such numbers when they enter the country.

Many countries issued such numbers ostensibly for a singular purpose, but over time, they become a de facto national identification number. For example, the United States originally developed its Social Security Number system as a means of disbursing Social Security benefits. Due to functionality creep, the number has become utilized for other purposes to the point where it is almost essential to have one in order to, among other things, open a bank account, obtain a credit card, or drive a car.

In the PRC, an ID card is mandatory for all citizens who are over 16 years old. The ID number has 18 digits and is in the format RRRRRRYYYYMMDDSSSC, which is the sole and exclusive identification code for the holder (an old ID card only has 15 digits in the format RRRRRRYYMMDDIII). RRRRRR is a standard code for the political division where the holder is born (county or a district of a city), YYYYMMDD is the birth date of the holder, and SSS is a sequential code for distinguishing people with identical birthdates and birthplaces. The sequential code is odd for males and even for females. The final character, C, is a checksum value over the first 17 digits. To calculate the checksum, each digit in order is multiplied by a weight in the ordered set [7 9 10 5 8 4 2 1 6 3 7 9 10 5 8 4 2] and summed together. The sum modulus 11 is used as an index into the ordered set [1 0 X 9 8 7 6 5 4 3 2], with the first index being zero. The indexed value is the checksum digit. In 15 digit IDs, III is an identification number created through certain mathematical methods (the last digit might be an English letter, such as X). The ID card is used for residential registration, army enrollment registration, registration of marriage/divorce, going abroad, taking part in various national exams, and other social or civil matters.

Source: http://en.wikipedia.org/wiki/National_identification_number