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# NAME

CheckDigits::M97_001 - compute check digits for VAT Registration Number (BE)

# SYNOPSIS

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

\$ustid = CheckDigits('ustid_be');

if (\$ustid->is_valid('136695962')) {
# do something
}

\$cn = \$ustid->complete('1366959');
# \$cn = '136695962'

\$cd = \$ustid->checkdigit('136695962');
# \$cd = '62'

\$bn = \$ustid->basenumber('136695962');
# \$bn = '1366959'
``````

# DESCRIPTION

## ALGORITHM

1. The whole number (without checksum) is taken modulo 97.

2. The checksum is difference of the remainder from step 1 to 97.

## METHODS

is_valid(\$number)

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

A leading 'BE' before the numbers will be ignored.

Returns false otherwise,

complete(\$number)

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

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

A leading 'BE' before the digits is ignored for the computation and retained for the result.

basenumber(\$number)

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

A leading 'BE' before the digits will be ignored and not returned with the result.

Return '' otherwise.

checkdigit(\$number)

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

Return '' otherwise.

None by default.

# AUTHOR

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