---
name: "Algorithm::CheckDigits::M11_013"
section: "3pm"
platform: "linux"
package: "libalgorithm-checkdigits-perl"
version: "1.3.6-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Algorithm::CheckDigits::M11_013"
---

# Algorithm::CheckDigits::M11\_013(3pm)

compute check digits for VAT Registration Number (GR)

## NAME

CheckDigits::M11\_013 - compute check digits for VAT Registration Number (GR)

## SYNOPSIS

```
  use Algorithm::CheckDigits;
  $ustid = CheckDigits('ustid_gr');
  if ($ustid->is_valid('123456783')) {
        # do something
  }
  $cn = $ustid->complete('12345678');
  # $cn = '123456783'
  $cd = $ustid->checkdigit('123456783');
  # $cd = '3'
  $bn = $ustid->basenumber('123456783');
  # $bn = '12345678';
```

## DESCRIPTION

### ALGORITHM

- 1\.

  Beginning right with the digit before the checkdigit all digits are weighted with 2 \*\* position. I. e. the last digit is multiplied with 2, the next with 4, then 8 and so on.

- 2\.

  The weighted digits are added.

- 3\.

  The sum from step 2 is taken modulo 11.

- 4\.

  If the sum from step 3 is greater than 9, the check sum is 0 else it is the sum itself.

### METHODS

- is\_valid($number)

  Returns true only if `$number` consists solely of numbers and the rightmost digit is a valid check digit according to the algorithm given above.

  Returns false otherwise,

- complete($number)

  The check digit for `$number` is computed and appended to the end of `$number`.

  Returns the complete number with check digit or '' if `$number` does not consist solely of digits.

- basenumber($number)

  Returns the basenumber of `$number` if `$number` has a valid check digit.

  Return '' otherwise.

- checkdigit($number)

  Returns the check digits of `$number` if `$number` has valid check digits.

  Return '' otherwise.

### EXPORT

None by default.

## AUTHOR

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

## SEE ALSO

perl, CheckDigits, *www.pruefziffernberechnung.de*,