Personal identity number (Sweden)

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The personal identity number (Swedish: personnummer) is the Swedish national identification number. When it was introduced in 1947 it was probably the first of its kind covering the total population. It is issued by the Swedish Tax Agency (Swedish: Skatteverket) as part of the Population Register (Swedish: Folkbokföring).

The personal identity number consists of 10 digits and a hyphen. The first six correspond to the person's birthday, in YYMMDD form. They are followed by a hyphen. People over the age of 100 replace the hyphen with a plus sign. The seventh through ninth are a serial number. An odd number is assigned to men, an even number to women. In some counties, such as Stockholm, they have started using 12 digit numbers to allow YYYYMMDD. This format is also used on official Swedish ID-cards.

The tenth digit is a checksum which was introduced in 1967 when the system was computerized. Originally, when the personal identity number was introduced, it had nine digits and the seventh and eighth denoted the county (Swedish: län) in which the subject was born. The seventh digit was 9 for foreign born. This system was replaced with the current system in 1990. Everyone however keeps their number and it is not hard to find out someone's number if you know the birth date, the birth county and the checksum algorithm. There are sites on the net where one can get public information about anyone, including credit ratings and debts [1].

People who have no Swedish personal identity number can receive a co-ordination number (Swedish: samordningsnummer) instead. It is issued by the Tax Agency at the request of a public agency. It is used for contact between a person and an agency which would otherwise require the use of a personal identity number. It is structured along the same lines, but with the day in the date of birth advanced by 60 (giving a number between 61 and 91).

Also, all organisations and companies have organisation numbers (Swedish: organisationsnummer). They look like personal identity numbers but have a "month" number of 20 or higher. They are used for tax purposes etc and have to be printed on receipts.

To calculate the checksum, multiply the individual digits in the identity number and 212121-212. The resulting products (a two digit product, such as 16, would be converted to 1 + 6) are added together. The checksum is 10 minus the ones place digit in this sum.

[edit] Example checksum

811218-987 gives

$\left [\begin{matrix}\underbrace{8 \cdot 2 = 16}\\1+6\to 7\end{matrix} \right ] + 1 + 2 + 2 + 2 + 8 + \left [\begin{matrix}\underbrace{9 \cdot 2 = 18}\\1+8\to 9\end{matrix} \right ] + 8 + \left [\begin{matrix}\underbrace{7 \cdot 2 = 14}\\1+4\to 5\end{matrix} \right ] = 44$