Business::DK::CPR - Danish CPR (SSN) number generator/validator


This documentation describes version 0.17


    use Business::DK::CPR qw(validate);

    my $rv;
    eval { $rv = validate(1501721111); };

    if ($@) {
        die "Code is not of the expected format - $@";

    if ($rv) {
        print 'CPR is valid';
    } else {
        print 'CPR is not valid';

    use Business::DK::CPR qw(calculate);

    my @cprs = calculate(150172);

    my $number_of_valid_cprs = calculate(150172);

    #Using with Params::Validate
    #See also examples/

    use Params::Validate qw(:all);
    use Business::DK::CPR qw(validateCPR);

    sub check_cpr {
        validate( @_,
        { cpr =>
            { callbacks =>
                { 'validate_cpr' => sub { validateCPR($_[0]); } } } } );

        print $_[1]." is a valid CPR\n";



CPR stands for Central Person Registration and is the social security number used in Denmark.


All methods are exported by explicit request. None are exported implicitly.


This function checks a CPR number for validity. It takes a CPR number as argument and returns:

  • 1 (true) for valid male CPR number

  • 2 (true) for a valid female CPR number

  • 0 (false) for invalid CPR number

It dies if the CPR number is malformed or in any way unparsable, be aware that the 6 first digits are representing a date (SEE: _checkdate function below).

In brief, the date indicate the person's birthday, the last 4 digits are representing a serial number and control cipher.

For a more thorough discussion on the format of CPR numbers please refer to the SEE ALSO section.

validate1968 is the old form of the CPR number. It is validated using modulus 11.

The new format introduced in 2001 (put to use in 2007, hence the name used throughout this package) can be validated using validate2007 and generate using generate2007.

The validate subroutine wraps both validators and checks using against both.

The generate subroutine wraps both generators and accumulated the results.

NB! it is possible to make fake CPR numbers that appear valid, please see MOTIVATION and the "calculate" function.

validate is also exported as: validateCPR, which is less imposing.


Better name for export. This is just a wrapper for "validate"


Validation against the original CPR algorithm introduced in 1968.


Validation against the CPR algorithm introduced in 2007.


This is a wrapper around calculate, so the naming is uniform to Business::DK::CVR

This function takes an integer representing a date and calculates valid CPR numbers for the specified date. In scalar context returns the number of valid CPR numbers possible and in list context a list of valid CPR numbers.

If the date is malformed or in any way invalid or unspecified the function dies.


Specialized generator for validate1968 compatible CPR numbers. See: generate


Specialized generator for validate2007 compatible CPR numbers. See: generate


See generate and generate1968. This is the old name for generate1968. It is just kept for backwards compatibility and it calls generate.


Mimics Hash::Merge's merge function. Takes two references to hashes and returns a single reference to a hash containing the merge of the two with the left parameter having precedence. The precedence has not meaning on the case in this module, but then the behaviour is documented.



This function validates the length of the argument, it dies if the argument does not fit within the boundaries specified by the arguments provided:

The _length function takes the following arguments:

number (mandatory), the number to be validated
length required of number (mandatory)


This subroutine takes a digit integer representing a date in the format: DDMMYY.

The date is checked for definedness, contents and length and finally, the correctness of the date.

The subroutine returns 1 indicating true upon successful assertion or dies upon failure.


This subroutine takes a 6 digit integer representing a date in the format: DDMMYY.

The subroutine returns 1 indicating true upon successful check or dies upon failure.


This subroutine takes an 10 digit integer representing a complete CPR. The CPR is tested for definedness, contents and length.

The subroutine returns 1 indicating true upon successful assertion or dies upon failure.


Business::DK::CPR exports on request:


  • 'argument for birthdate should be provided', a data parameter has to be provided.

    This error is thrown from _checkdate, which is used for all general parameter validation.

  • 'argument: <birthdate> could not be parsed', the date provided is not represented by 6 digits (see also below).

    This error is thrown from _checkdate, which is used for all general parameter validation.

  • 'argument: <birthdate> has to be a valid date in the format: ddmmyy', the date format used for CPR numbers has to adhere to ddmmyy in numeric format like so: 311210, day in a two digit representation: 01-31, month also two digit representation: 01-12 and finally year in a two digit representation: 00-99.

    This error is thrown from _checkdate, which is used for all general parameter validation.

  • 'Unknown gender: <gender>, assuming no gender', this is just a warning issued if a call to generate2007 has not been provided with a gender parameter



This module requires no special configuration or environment.


There are no known incompatibilies in this package.


  • Nothing to do, please refer to the distribution TODO file for the general wish list and ideas for future expansions and experiments.


The distribution uses the TEST_AUTHOR environment variable to run some additional tests, which are interesting to the the author, these can be disabled by not defining or setting the environment variable to something not positive.

The distribution uses the TEST_CRITIC environment variable to control Perl::Critic tests.


Here are listed the standard tests, recommended for all CPAN-like distributions. The matrix lists what flags are required to run the specific test.

    --------------- ---- ----------- ----------- --------
    00.load.t         *
    changes.t         *
    critic.t                              *
    kwalitee.t                *
    pod-coverage.t                                   *
    pod.t                                            *
    prerequisites.t           *
    --------------- ---- ----------- ----------- --------

All of the above tests are actually boilerplates and are maintained as separate components.


Coverage of the test suite is at 89.1% for release 0.04, the coverage report was generated with the TEST_AUTHOR flag enabled (SEE: TEST AND QUALITY)

    ---------------------------- ------ ------ ------ ------ ------ ------ ------
    File                           stmt   bran   cond    sub    pod   time  total
    ---------------------------- ------ ------ ------ ------ ------ ------ ------
    blib/lib/Business/DK/    74.2   41.9   53.8  100.0  100.0   72.9   70.3
    .../Class/Business/DK/   89.1   85.7   77.8   71.4  100.0   27.1   86.0
    Total                          77.6   50.0   63.6   91.3  100.0  100.0   74.1
    ---------------------------- ------ ------ ------ ------ ------ ------ ------


This section describes use of Perl::Critic from a perspective of documenting additions and exceptions to the standard use.


No known bugs at this time.

Business::DK::CPR has some obvious flaws. The package can only check for validity and format, whether a given CPR has been generated by some random computer program and just resemble a CPR or whether a CPR has ever been assigned to a person is not possible without access to central CPR database an access, which is costly, limited and monitored.

There are no other known limitations apart from the obvious flaws in the CPR system (See: SEE ALSO).


Please report issue via GitHub

Alternatively report issues via CPAN RT:

or by sending mail to




I write business related applications. So I need to be able to validate CPR numbers once is a while, hence the validation function.

The calculate/generate1968 function is however a different story. When I was in school we where programming in Comal80 and some of the guys in my school created lists of CPR numbers valid with their own birthdays. The thing was that if you got caught riding the train without a valid ticket the personnel would only check the validity of you CPR number, so all you have to remember was your birthday and 4 more digits not being the actual last 4 digits of your CPR number.

I guess this was the first hack I ever heard about and saw - I never tried it out, but back then it really fascinated me and my interest in computers was really sparked.


  • Jonas B., (jonasbn) - <>


  • Karen Etheridge (ETHER)

  • Neil Bowers (NEILB)

  • Mohammad S Anwar (MANWAR)


Business-DK-CPR and related is (C) by Jonas B., (jonasbn) 2006-2020


Business-DK-CPR is released under the Artistic License 2.0