# NAME

CheckDigits::MXX_004 - compute check digits for VAT RN (AT)

# SYNOPSIS

use Algorithm::CheckDigits;

\$vat = CheckDigits('ustid_at');

if (\$vat->is_valid('U13585627')) {
# do something
}

\$cn = \$vat->complete('U1358562');
# \$cn = 'U13585627'

\$cd = \$vat->checkdigit('U13585627');
# \$cd = '7'

\$bn = \$vat->basenumber('U13585627');
# \$bn = 'U1358562'

# DESCRIPTION

## ALGORITHM

1. Beginning right all numbers before the check digit are weighted alternatively 1 and 2.

2. The total of the digits of all products is computed and then subtracted from 96.

3. The check digit is the sum of step 3 taken modulo 10.

## METHODS

is_valid(\$number)

Returns true only if \$number consists solely of numbers and the last 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 concatenated to the end of \$number.

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

basenumber(\$number)

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

Return '' otherwise.

checkdigit(\$number)

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

Return '' otherwise.

None by default.

# AUTHOR

Mathias Weidner, <mamawe@cpan.org>