Sweden

The format is YYMMDD-NNGC. Where the first six give the birth date in YYMMDD format. Digits seven to nine (NNG) are used to make the number unique, where digit nine (G) is odd for men and even for women. For numbers issued before 1990, the seventh and eighth digit identify the county of birth or foreign-born people, but privacy-related criticism caused this system to be abandoned for new numbers. The tenth digit (C) is created using the Luhn, or "mod 10", checksum algorithm.

Finland

The format is DDMMYY-NNNT (where D (day), M (month), Y (year) and N is all numbers and T is a control character either a number OR a letter). We haven't seen any other format here, but according to the specifications there are 3 alternative formats: DDMMYYNNNT, DDMMYY+NNNT and DDMMYYANNNT. Assently directly return it the way the banks send it.

Denmark

The CPR number is a ten-digit number with the format DDMMYY-SSSS, where DDMMYY is the date of birth and SSSS is a sequence number. The first digit of the sequence number encodes the century of birth (so that centenarians are distinguished from infants, 0-4 in odd centuries, 5-9 in even centuries), and the last digit of the sequence number is odd for males and even for females.

Note: NemID does not provide National ID (CPR/CVR) with response but if you send CPR along with request they can validate it.

Norway

Formated as DDMMYYXXXXXX.

The number has been composed of the date of birth (DDMMYY), a three digit individual number, and two check digits. The individual number and the check digits are collectively known as the Personal Number.

More information about ID numbers in different countries can be found on Wikipedia: National Identification Number.