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ssin : Belgian national identification numbers

The lino.utils.ssin module defines some utilities for manipulating Belgian national identification numbers.

Lines starting with >>> in this document are code snippets that get tested as part of our development workflow.

>>> from lino import startup
>>> # lino.startup('lino.projects.std.settings_test')
>>> startup('lino_book.projects.min1.settings')
>>> from lino.api.doctest import *

Which means that code examples in this document use the lino_book.projects.min1 demo project.

We will also use some additional Python modules:

>>> import datetime


Belgians call their national identification number INSZ (“identificatienummer van de sociale zekerheid) in Dutch, NISS (“No. d’identification de Sécurité Sociale”) in French or INSS (“Identifizierungsnummer der Sozialen Sicherheit”) in German. We use the English abbreviation SSIN (“Social Security Identification Number”), though some sources also speak about INSS (“Identification Number Social Security”).

See also


The module defines the functions format_ssin() and new_format_ssin().

>>> from lino.utils.ssin import Genders
>>> from lino.utils.ssin import format_ssin, new_format_ssin

An officialy obsolete but still used format for printing a Belgian SSIN is YYMMDDx123-97, where YYMMDD is the birth date, x indicates the century (* for the 19th, a space for the 20th and a = for the 21st century), 123 is a sequential number for persons born the same day (odd numbers for men and even numbers for women), and 97 is a check digit (remainder of previous digits divided by 97).


The module defines two validator functions, is_valid_ssin() and ssin_validator().

>>> from lino.utils.ssin import ssin_validator, is_valid_ssin

The difference between them is that one returns True or False while the other raises a ValidationError to be used in Django forms. The message of this ValidationError depends on the user language.

>>> ssin_validator('123') 
Traceback (most recent call last):
ValidationError: [u'Invalid SSIN 123 : A formatted SSIN must have 13 positions']
>>> is_valid_ssin('123')

Generating fictive SSIN

The module also defines a function generate_ssin() is mainly used to generate fictive demo data. For example, here is the national number of the 25th boy born in Belgium on June 1st, 1968:


>>> from lino.utils.ssin import generate_ssin
>>> n = generate_ssin(datetime.date(1968, 6, 1), Genders.male, 53)
>>> print(n)
680601 053-29
>>> ssin_validator(n)

The sequence number is optional and the default value depends on the gender. For boys it is 1, for girls 2.

>>> n = generate_ssin(datetime.date(2002, 4, 5),Genders.female)
>>> print(n)
020405 002=44
>>> ssin_validator(n)
>>> n = generate_ssin(datetime.date(1968, 7, 21), Genders.male, 13)
>>> print(n)
680721 013-58
>>> ssin_validator(n)

SSIN for incomplete birth date

Here is the SSIN of a person with incomplete birth date:

>>> from lino.utils import IncompleteDate
>>> n = generate_ssin(IncompleteDate(1995, 0, 0), Genders.male, 153)
>>> print (n)
950000 153-96
>>> ssin_validator(n)

No need for special characters?

In 1983 Belgians discovered that the formatting with a special character to indicate the century is not absolutely required since the national register no longer cared about people born before 1900, and now the century can be deduced by trying the check digits.

>>> format_ssin('68060105329')
'680601 053-29'

In order to say whether the person is born in 19xx or 20xx, we need to look at the check digits.

For example, the 25th boy born on June 1st in 1912 will get another check-digit than a similar boy exactly 100 years later (in 2012):

>>> format_ssin('12060105317')
'120601 053-17'
>>> format_ssin('12060105346')
'120601 053=46'

Question to mathematicians: is it sure that there is no combination of birth date and sequence number for which the check digits are the same?