Portuguese Bank Account Number (NIB)

Nowadays it is quite common for people to have to provide their NIB (Bank Account Number) to various institutions as, for example, the employer and Tax Services. Perhaps most people, afraid of making some error (after all, the number has 21 digits), checks it over several times: usually, it is to receive money ... and nobody wants the money to end up in someone else's account.

But have you ever heard someone complain that their money ended up in someone else's account? Most likely not. Why? Are people so cautions that an error never occurs? Not even with the administrative staff that receive the data and have to handle with hundreds of numbers? Or rather, is there something that prevents the possible ocurrence of errors?

Yes, indeed there is something: NIB numbers are designed with two supplementary check digits that prevent most ocurrence of errors (at least, the most common ones, so that the chance of sending the money to a different account holder is very small).

When someone opens a new account in a bank, the account is identified by a number with twenty-one digits, of which the last two (the check digits) are completely determined by the first nineteen (that identify the Bank, the Bank branch, the type of account and the account).

You may see here how the two check digits are calculated.