Verifies a given
"NIF", the Número de Identificação Fiscal,
the Portuguese VAT (value-added tax) number.
In a valid NIF, the 9.th digit is a check digit,
a certain function of all the other, previous digits.
The NIF given can be a valid one, for verification,
or any value, for computing of the (last) check digit. Note that
not all numbers make it possible to find a valid check digit
(i.e., between 0 and 9).
A graph is shown for the progressive values
(one for each digit) involved. |
