Finnish ID validation

Owned by Valentyna Plokhykh, created
Last updated: May 09, 2023 by Sigrid Kviteberg

The article explains the logic and structure of the Finnish Personal Identification Number, and how each user can turn on the validation when entering a new person.

Introduction

Finnish Personal ID consists of 11 characters generated by a specific logic.

Code Structure

1-6. Date of Birth

The ID starts with the day, month, and year of birth, in the format DDMMYY.

For example, if the date of birth is the 13th of October 1952, then the Personal ID will start with 131052.

7. The sign indicating the century of birth

The sign after the date of birth indicates in which century the person was born:

  • In the 1900s can be a hyphen “-”, Y, X, W, V, and U;

  • In the 2000s can be A, B, C, D, E, and F;

  • In the 1800s can be only a plus “+”.

8-10. Individual number

Individual numbers consist of 3 digits issued by the government. Men have an odd number and women an even number. In practice, all individual numbers issued are within the range of 002 to 899. 

11. Control character

The control character can be a number or a letter. It is obtained by dividing the nine-digit number consisting of the date of birth and the individual number by 31. 

The control character is determined on the basis of the remainder according to the table below.

When the remainder corresponding to the control character in the personal identity code is calculated and the calculation returns a decimal number, the remainder is established as follows: the decimals following the whole number are multiplied by 31 and the resulting number is rounded to the nearest whole number. The following example illustrates the method: 

The personal identity code is 131052-308T. The T is arrived at by taking the number 131052308 and dividing it by 31. The result of the division, depending on the precision of the calculator, may appear as e.g. 4227493.8064516129032258064516129. 

Taking the number series .8064516129032258064516129 appearing after the decimal point and multiplying it by 31 gives the result of 24.9999999999999999999999999, which rounded to the nearest whole number is 25. The table of corresponding control characters then provides the T in the personal identity code. 

Validation

To enable the validation of Personal ID, the user must turn ON the user option “Check Person ID validity”

If the entered ID does not match the validation criteria, the user will receive the message as below, the system would still allow saving the ID with the user’s consent.