The IBAN (International Bank Account Number) is a standardised structure for payment account identifiers. It has become an internationally accepted standard with the publication of ISO 13616.

The IBAN is constructed from the BBAN (Basic Bank Account Number) adopted in each country, preceded by the respective country code and two check digits. 

In the particular case of payment accounts domiciled in Portugal, the IBAN is composed of the NIB (Banking Identification Number), corresponding to the Portuguese BBAN, preceded by the country code (‘PT’) and two check digits (in Portugal’s case, these digits are always ‘50’).