What is an IBAN and how do its check digits work?

IBAN stands for International Bank Account Number. It is one long code that names a single bank account in a way that banks in other countries can read without knowing the local system. It does not replace the account number: it wraps the local bank code and account number in a standard cover.

The four parts

1. Country code: two letters, such as DE for Germany.
2. Check digits: two digits worked out from all the other characters. They catch typing mistakes.
3. Bank part: the code of the bank and, in some countries, of the branch.
4. Account part: the account number, sometimes with a national check digit of its own.

Parts 3 and 4 together are called the BBAN (Basic Bank Account Number). Each country decides its own BBAN layout and length, which is why IBANs run from 15 characters (Norway) to 33 (Russia). The standard allows up to 34.

A made-up German example, split into its parts:

• DECountry
• 43Check digits
• 12345678Bank code
• 9012345678Account number

How the check digits are tested

Anyone can test an IBAN with simple arithmetic. Using the made-up example DE43 1234 5678 9012 3456 78:

1. Move the first four characters to the end: 123456789012345678DE43.
2. Replace each letter with a number: A is 10, B is 11, and so on up to Z, which is 35. D becomes 13 and E becomes 14: 123456789012345678131443.
3. Divide this long number by 97. If the remainder is exactly 1, the IBAN passes. Here the remainder is 1.

If one character is typed wrongly, or two neighbours are swapped, the remainder is almost never 1, so the mistake is caught before money moves.

What a passing check does not tell you

• It does not show that the account exists or is open.
• It does not show who owns the account.
• It does not protect against fraud: a cheat can give you a perfectly valid IBAN of their own account.

So always get the IBAN from the person or company you are paying, through a channel you trust.

Where to find your own IBAN

If your bank is in a country that uses IBAN, it is printed on your bank statement and shown in online or mobile banking, and in some countries on the bank card. Do not build it yourself from the account number; ask the bank. Banks in India, the United States and many other countries do not issue IBANs at all: see what to use there.

Checked in November 2026. IBAN is defined by the international standard ISO 13616; SWIFT keeps the registry of country layouts.

Check an IBAN Formats by country