IBAN Format by Country

What Is a BBAN?

The BBAN (Basic Bank Account Number) is the portion of an IBAN that follows the country code and check digits. It contains all the domestic banking identifiers needed to route a payment within a specific country: bank code, branch code (where applicable), and account number. The BBAN format is defined independently by each country's banking authority, which is why IBAN lengths differ so much from one country to another.

For example, a German BBAN is 18 digits (8-digit bank code followed by a 10-digit account number), while a Norwegian BBAN is only 11 digits (4-digit bank code, 6-digit account number, and 1 check digit). The IBAN standard simply adds a uniform CC (country code) + kk (check digits) prefix to whatever domestic format the country already uses. This means the total IBAN length equals 4 (country code + check digits) plus the BBAN length for that country.

How to Read the Format Notation

The format column in the table below uses letter codes to indicate which part of the domestic banking structure each character position represents. Understanding this notation is essential if you need to manually verify or construct an IBAN. Here is what each letter means:

As a quick example, the German format DEkk BBBB BBBB CCCC CCCC CC tells you that after the country code (DE) and check digits (kk), there are 8 bank-code digits (B) followed by 10 account-number digits (C), for a total of 22 characters.

IBAN Length and Format Table

In the format column: kk = check digits, B = bank code, S/G = sort/branch code, C = account number, K = national check digit, X = national check letter. For a complete list of every country that uses IBANs, see our which countries use IBAN guide.

Why IBAN Lengths Differ

One of the most common IBAN errors is having the wrong number of characters. Each country defines a fixed length — a German IBAN is always exactly 22 characters and a French IBAN is always exactly 27. Adding or removing a digit will cause the MOD-97 check to fail, and the transfer will be rejected.

The variation in length exists because IBANs wrap each country's pre-existing domestic account format. Countries with longer domestic numbers (such as bank code + branch code + account number + national check digits) produce longer IBANs. Norway, whose domestic format consists of just an 11-digit account number, has the shortest IBAN at 15 characters. Malta and other countries with more complex domestic structures can have IBANs up to 31 or even 34 characters.

This is precisely why validation matters: if you are expecting a German IBAN and receive a 27-character string, something is wrong. The length alone can tell you whether the IBAN matches the claimed country of origin. Our validator checks this automatically, but it is useful to know the expected lengths for the countries you deal with most often.

Letters in the Account Part

A frequent question is whether IBANs can contain letters in the account number portion. The answer depends on the country. In most countries (Germany, France, Spain, Italy, Norway, etc.), the BBAN is entirely numeric — it consists only of digits. However, some countries allow or require alphabetic characters in parts of the BBAN.

The United Kingdom is a common example: the BBAN starts with a four-letter bank code (such as NWBK for NatWest or LOYD for Lloyds), followed by numeric sort code and account number digits. The Netherlands also uses a four-letter bank identifier (INGB, ABNA, RABO, etc.) in its BBAN. In these cases, the letters are always in the bank code portion, not the account number itself. Some countries in the Middle East, such as Kuwait and Bahrain, also permit alphanumeric characters in certain BBAN positions.

The SWIFT IBAN Registry specifies for each country whether each position in the BBAN must be numeric (n), alphabetic (a), or alphanumeric (c). When validating or constructing an IBAN, always check the character-type rules for the specific country.

Handling IBANs With and Without Spaces

IBANs can be presented in two forms: the "print" format with spaces every four characters (e.g., DE89 3704 0044 0532 0130 00) and the "electronic" format without any spaces (e.g., DE89370400440532013000). Both represent the same IBAN. The print format is used on paper documents, invoices, and bank statements for human readability. The electronic format is what payment systems and banking software use internally.

When entering an IBAN into a payment form, most modern banking interfaces accept both formats and strip spaces automatically. However, older systems, APIs, and some third-party payment processors may reject an IBAN that contains spaces. As a best practice, always store IBANs in electronic format (no spaces) and only add spaces when displaying them to humans. When counting characters to check the length, make sure to exclude any spaces first.

Common Format Mistakes by Country

Different countries have different patterns of errors that people commonly make. Being aware of these can save time and prevent failed payments:

• Germany (DE, 22 chars): The 8-digit bank code (Bankleitzahl) is sometimes confused with the older 3-digit bank group code. Ensure you use the full 8-digit BLZ. Account numbers shorter than 10 digits must be padded with leading zeros.
• United Kingdom (GB, 22 chars): The four-letter bank code is alphabetic, not numeric. Confusing it with the sort code is a common error. Remember: bank code (4 letters) + sort code (6 digits) + account number (8 digits).
• France (FR, 27 chars): French IBANs include two national check digits (RIB key) at the end. Omitting these makes the IBAN too short and invalid. Also, the account number portion in France can contain both digits and letters in some cases.
• Spain (ES, 24 chars): Spanish IBANs include two national check digits between the branch code and the account number. These are sometimes omitted or confused with the IBAN-level check digits.
• Netherlands (NL, 18 chars): The four-letter bank code must be uppercase. Using lowercase letters may cause validation failures in strict systems. Account numbers shorter than 10 digits must be padded with leading zeros.
• Italy (IT, 27 chars): Italian IBANs begin the BBAN with a single check letter (CIN), which is an alphabetic character computed from the remaining domestic digits. Omitting this letter shortens the IBAN to 26 characters and causes validation to fail.
• Norway (NO, 15 chars): Norwegian IBANs are the shortest at just 15 characters. People accustomed to longer IBANs sometimes assume a Norwegian IBAN is incomplete and try to add characters, which invalidates it.

Frequently Asked Questions

Why are IBANs different lengths?

Each country's IBAN length is determined by the length of its domestic account numbering system. The IBAN wraps the existing domestic format (bank code, branch code, account number, and any national check digits) with a standard country code and two check digits. Countries with longer domestic numbers produce longer IBANs. Norway has the shortest at 15 characters because its domestic format is compact, while Malta can reach 31 characters due to its more detailed structure.

Can an IBAN have letters in the account part?

It depends on the country. In most countries, the account number portion of the BBAN is purely numeric. However, some countries include alphabetic characters in their BBAN — for example, the United Kingdom and the Netherlands use four-letter bank codes within the BBAN. The SWIFT IBAN Registry specifies for each country whether each BBAN position is numeric, alphabetic, or alphanumeric.

What does "kk" mean in the format?

The kk in an IBAN format represents the two check digits, which are always positions 3 and 4 of the IBAN. These are calculated using the MOD-97 algorithm defined in ISO 7064 and serve as an error-detection mechanism. When you see a format like DEkk BBBB BBBB CCCC CCCC CC, the kk will be replaced by two specific digits (like 89 in DE89) that validate the rest of the IBAN.

How do I know which format to expect?

The first two characters of any IBAN are the ISO 3166-1 alpha-2 country code (DE for Germany, GB for the United Kingdom, FR for France, and so on). Once you identify the country code, you can look up the expected length and format in the table above or in the SWIFT IBAN Registry. If the IBAN you have received does not match the expected length for its country code, it is likely invalid.

Check Your IBAN Format

Paste any IBAN into our IBAN validator to instantly verify it matches the correct country format. The tool checks the length, structure, and checksum, and shows a breakdown of the bank code, branch, and account number. All validation runs entirely in your browser — no data is sent to any server.