# NAME

CheckDigits::M11_011 - compute check digits for VAT Registration Number (NL)

# SYNOPSIS

``````  use Algorithm::CheckDigits;

\$ustid = CheckDigits('ustid_nl');

if (\$ustid->is_valid('123456782')) {
# do something
}
if (\$ustid->is_valid('123456782B04')) {
# do something
}

\$cn = \$ustid->complete('12345678');
# \$cn = '123456782'
\$cn = \$ustid->complete('12345678.B04');
# \$cn = '123456782B04'

\$cd = \$ustid->checkdigit('123456782');
# \$cd = '2'
\$cd = \$ustid->checkdigit('123456782B04');
# \$cd = '2'

\$bn = \$ustid->basenumber('123456782');
# \$bn = '12345678';
\$bn = \$ustid->basenumber('123456782B04');
# \$bn = '12345678.B04';
``````

# DESCRIPTION

This VATRN has 12 "digits", the third last must be a B, the fourth last is the checkdigit. I don't know anything about the meaning of the last two digits.

You may use the whole VATRN or only the first eight digits to compute the checkdigit with this module.

## ALGORITHM

1. Beginning right with the digit before the checkdigit all digits are weighted with their position. I.e. the digit before the checkdigit is multiplied with 2, the next with 3 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 10, the number is discarded.

## METHODS

is_valid(\$number)

Returns true only if the first eight positions of `\$number` consist solely of digits (maybe followed by 'B' and to further digits) and the eighth 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 inserted at position eight of `\$number`.

Returns the complete number with check digit or '' if `\$number` does not consist solely of digits a dot and maybe 'B' at the ninth position.

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.

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