In Finland, the personal identity code (Finnish: henkilötunnus (HETU), Swedish: personbeteckning), also known as personal identification number, is used for identifying the citizens in many government and civilian systems. It uses the form DDMMYYCZZZQ, where DDMMYY is the date of birth, C is the century identification sign (+ for the 19th century, - for the 20th and A for the 21st), ZZZ is the personal identification number (odd number for males, even number for females) and Q is a checksum character. For example, a valid henkilötunnus is 311280-999J.

The checksum character is calculated thus: Take the birth date and person number, and join them into one 9-digit number x. Let n = x mod 31. Then the checksum letter is the (n+1)th character from this string: "0123456789ABCDEFHJKLMNPRSTUVWXY".

The use of the personal ID number is regulated, and requesting is legally restricted. Often it is needed for government transactions. Contrary to popular belief, the ID number is displayed in some public documents (such as the deed of purchase of real estate) and should not be used for identification. It is problematically treated much like a proof of identity in many contexts, such as health care. When given the choice, it is hence advisable not to make it public. Employers often track salaries using the number. The number is given shortly after birth, and it is also possible for foreigners to get one for purposes of employment registration.

The number is shown in all forms of valid identification:

  • National ID card
  • Electronic national ID card (with a chip)
  • Driver's license (old A6-size and new credit card-size)
  • Passport

The personal identity code was formerly known as sosiaaliturvatunnus (SOTU, Social Security number).

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