# Kennitala

The kennitala (plural: kennitölur; abbreviated kt.) (English: Identity Number) is a unique national identification number used by the Icelandic government to identify individuals and organisations in Iceland, administered by the Registers Iceland. Kennitölur are issued to Icelandic citizens at birth, and to foreign nationals resident in Iceland upon registration.[1] They are also issued to corporations and institutions.

## Number derivation

Kennitölur are composed of ten digits. For a personal kennitala, the first six of these are the individual's date of birth in the format DDMMYY.[1] The seventh and eighth digits are randomly chosen (although the seventh number must be larger or equal to 2) when the kennitala is allocated, the ninth is a check digit, and the tenth indicates the century of the individual's birth: '9' for 1900–1999, '0' for 2000 and beyond. Kennitölur are often written with a hyphen following the first six digits, e.g. 120174-3399.
D1D2M1M2Y1Y2R1R2CM
D = day, M = Month, Y = year, R = random, C = checksum, M = millennium.

The check digit equations is:
C = 11 - ((3xD1 + 2xD2 + 7xM1 + 6xM2 + 5xY1 + 4xY2 + 3xR1 + 2xR2) mod 11)

The consequence of this design is that no more than 79 people can be born on the same day. The exact same formula is used for the identification numbers of organisations and companies, instead of the date of birth the initial registration date is used and then the number 4 is added to the first digit to makes sure there are no conflicts with individuals.

## Use

The system is similar to that employed by some other European countries, but Iceland makes unusually extensive and public use of its kennitölur, with businesses and educational institutions eschewing internal identification numbers in favour of the national system, and its use being mandated in banking transactions. Furthermore, online banking services in Iceland offer a lookup service to check names against numbers. Because of their public nature, kennitölur are not used for authentication. The completeness of the National Register has eliminated the need for the country to conduct a regular census: population statistics can be obtained by simply querying the database.