NAME

       CheckDigits::M23_002 - compute check digits for Tax Identification Number (IE)

SYNOPSIS

         use Algorithm::CheckDigits;

         $dni = CheckDigits('tin_ie');

         if ($dni->is_valid('8473625E')) {
               # do something
         }

         $cn = $dni->complete('1234567.W');
         # $cn = '1234567TW'

         $cd = $dni->checkdigit('1234577IA');
         # $cd = 'I'

         $bn = $dni->basenumber('1234577WW');
         # $bn = '1234577.W'

DESCRIPTION

   ALGORITHM
       The irish TIN (Tax Identification Number) or VAT Regstration Number consists of 7 digits, a letter in the
       range from 'A' - 'W' as checksum, and an optionally letter in the range from 'A' - 'I' or the letter 'W'.

       1.  In  reverse order, each digit is multiplied by a weight started at 2.  (i.e. the number left from the
           check digit is multiplied with 2, the next with 3 and so on).

       2.  If there is an optional letter following the checksum letter (position 9), this letter is mapped to a
           numeric value based on the following mapping: "A" = 1, "B" = 2, ... "H" = 8, "I" = 9. "W" or  absence
           of this letter means a value of 0. This numeric value is multiplied with 9.

       3.  All products from step 1 and 2 are added.

       4.  The  check  digit  is  the  sum  from step 3 modulo 23. This number is expressed as the corresponding
           letter from the alphabet where A-V correspond to 1-22 and W stands for check digit 0.

   METHODS
       is_valid($number)
           Returns true only if $number complies with the rules given above and there is a valid check digit  at
           position eight.

           Returns false otherwise,

       complete($number)
           The check digit for $number is computed and inserted at position eight of $number.

           Returns  the  complete number with check digit or '' if $number does not consist solely of digits and
           an optional letter at position nine.

       basenumber($number)
           Returns the basenumber of $number if $number has a valid  check  digit.  As  a  placeholder  for  the
           checksum  a  point ('.') is inserted at position eight when the checksum contains the optional letter
           at position nine.

           Return '' otherwise.

       checkdigit($number)
           Returns the checkdigit of $number if $number has a valid check digit.

           Return '' otherwise.

   EXPORT
       None by default.

AUTHOR

       Mathias Weidner, "<mamawe@cpan.org>"

SEE ALSO

       perl, CheckDigits, https://ec.europa.eu/taxation_customs/tin/

perl v5.36.0                                       2022-10-13               Algorithm::CheckDigits::M23_002(3pm)