The end of the BIN? Its role in the IBAN era

Key takeaways

Unique identification: The NIB (Bank Identification Number) is used to identify your account in domestic payments. Structure: It consists of 21 digits, including bank code, branch code, account number, and two control digits. Transition to IBAN: Since 2016, under SEPA rules, IBAN has replaced NIB as the mandatory standard for transfers. Direct relation: In Portugal, the IBAN is simply the prefix “PT50” followed by your 21-digit NIB. Tax Authority compliance: For invoicing and refunds from the Portuguese Tax Authority (AT), you should always keep your IBAN updated.

What is the NIB and what is it used for in your daily life?

The NIB (Bank Identification Number) is the numeric code that identifies your bank account in Portugal. Think of it as the digital “address” of your money within the national banking system.

Before European standardization, the NIB was the main tool for making transfers between Portuguese banks or setting up direct debits for bills like electricity or internet.

Although today you mostly hear about IBAN, the NIB still exists “inside” it. Its purpose is to ensure that the money you send or receive reaches the correct account, avoiding errors between financial institutions.

How is your account number structured?

The NIB is not random — it follows a strict 21-digit structure that can be broken down as follows:

1. Bank code (4 digits): Identifies the institution (e.g., 0033, 0035, etc.)
2. Branch code (4 digits): Indicates where the account was opened
3. Account number (11 digits): Your unique identifier within the bank
4. Control digits (2 digits): Used to mathematically validate the number and prevent errors

What is the difference between NIB and IBAN?

The difference lies in geography and format.

The NIB is used only for domestic operations within Portugal. The IBAN (International Bank Account Number) is the international standard that enables secure transfers across Europe (SEPA zone).

In Portugal, the conversion is simple: you take your 21-digit NIB and add the country code (PT) plus the European control digits (50). So, if you know your NIB, you already know your IBAN.

Why should your business use IBAN on invoices?

If you use Moloni ON to manage your business, you’ve likely noticed how important it is to configure your banking details correctly.

According to SEPA rules, IBAN is mandatory for all euro credit transfers and direct debits. By including your IBAN (instead of just the NIB) on certified invoices, you:

• Make payments easier: Clients can pay you from anywhere in Europe;
• Show professionalism: Your business aligns with current banking standards;
• Avoid rejections: Many banks no longer process payments using only NIB.

How can you validate if your NIB is correct?

A single wrong digit can result in sending money to the wrong account or having payments rejected.

The easiest way to validate your NIB is through your online banking or official bank documents. You may notice that the last two digits (control digits) change if any earlier number is altered.

This built-in validation system allows banking apps and invoicing software to immediately flag incorrect numbers before you confirm a transaction.

NIB and the Tax Authority: what do you need to know?

If you are self-employed or run a business, having your NIB/IBAN correctly registered on the Tax Authority portal is essential.

This is the account used by the Portuguese Tax Authority (AT) to process VAT or income tax refunds.

If you change your bank account, make sure to update it both on the portal and in your invoicing software. An outdated IBAN can delay payments and create unnecessary cash flow issues in your business.