An IBAN tells a bank exactly which account to credit, and two of its characters exist only to catch typing mistakes before the money leaves. This guide takes the standard example IBAN apart, lists lengths for 23 countries from SWIFT's registry, runs the check-digit test by hand with real numbers and covers what to do when, as in the US, there is no IBAN. The bank code that often travels with it is covered in SWIFT codes explained, and the rest of the transfer process in the money transfer hub.
What is an IBAN number?
An IBAN number, short for International Bank Account Number, is a code defined by the ISO 13616 standard that identifies one account at one institution in one country.
The current edition, ISO 13616-1:2020, caps the code at 34 characters. SWIFT has been the registration authority since 2006 and publishes every national format in its IBAN Registry, and only a country's national standards body or central bank can submit one. Release 103, from September 2026, covers 89 countries and territories: every country in the Single Euro Payments Area plus others such as Brazil, Costa Rica, Egypt, Pakistan, Saudi Arabia, Turkey and the United Arab Emirates. The United States, Canada, Australia, Mexico, India and China have no IBAN format.
The IBAN identifies the account, while a BIC, when one is needed, identifies the bank. SEPA is a payment scheme that uses IBANs; it is not the IBAN itself.
How is an IBAN put together?
Every IBAN has three parts: a two-letter country code, two check digits, and a basic bank account number (BBAN) whose length and layout are fixed for each country.
| Part | Characters | In GB29 NWBK 6016 1331 9268 19 | Meaning |
|---|---|---|---|
| Country code | 2 letters | GB | United Kingdom, from ISO 3166-1 |
| Check digits | 2 digits | 29 | Calculated from all the other characters |
| Bank identifier | 4 letters | NWBK | The bank's code |
| Branch identifier | 6 digits | 601613 | The UK sort code |
| Account number | 8 digits | 31926819 | The domestic account number |
That is the registry's published example for the UK. The registry writes the layout as GB2!n4!a6!n8!n, meaning 2 digits, then 4 letters, 6 digits and 8 digits, all of fixed length, for 22 characters in all. Because the bank identifier always sits in the same place for a given country, banks can look up the BIC from the IBAN alone. On paper IBANs are printed in groups of four; in payment files they are written without spaces, as GB29NWBK60161331926819. The country code is that of the country where the institution holding the account is located, which is not necessarily where the account holder lives.
How long is an IBAN in each country?
IBAN lengths run from 15 characters in Norway to 33 in Russia, and each country's length is fixed, so a code of the wrong length is always invalid.
| Country | Starts with | Length | After the check digits | SEPA country in the registry |
|---|---|---|---|---|
| Norway | NO | 15 | 11 digits | Yes |
| Belgium | BE | 16 | 12 digits | Yes |
| Netherlands | NL | 18 | 4 letters, 10 digits | Yes |
| Denmark | DK | 18 | 14 digits | Yes |
| Austria | AT | 20 | 16 digits | Yes |
| Switzerland | CH | 21 | 5 digits, 12 letters or digits | Yes |
| Germany | DE | 22 | 18 digits | Yes |
| United Kingdom | GB | 22 | 4 letters, 14 digits | Yes |
| Ireland | IE | 22 | 4 letters, 14 digits | Yes |
| Bulgaria | BG | 22 | 4 letters, 6 digits, 8 letters or digits | Yes |
| United Arab Emirates | AE | 23 | 19 digits | No |
| Spain | ES | 24 | 20 digits | Yes |
| Pakistan | PK | 24 | 4 letters, 16 letters or digits | No |
| Saudi Arabia | SA | 24 | 2 digits, 18 letters or digits | No |
| Portugal | PT | 25 | 21 digits | Yes |
| Turkey | TR | 26 | 6 digits, 16 letters or digits | No |
| France | FR | 27 | 10 digits, 11 letters or digits, 2 digits | Yes |
| Italy | IT | 27 | 1 letter, 10 digits, 12 letters or digits | Yes |
| Poland | PL | 28 | 24 digits | Yes |
| Brazil | BR | 29 | 8 letters or digits, 15 digits, 2 letters or digits | No |
| Egypt | EG | 29 | 25 digits | No |
| Malta | MT | 31 | 4 letters, 5 digits, 18 letters or digits | Yes |
| Russia | RU | 33 | 14 digits, 15 letters or digits | No |
The registry marks 37 of its 89 countries as SEPA members, which matters for the BIC question further down. A length check is the quickest test there is: a German IBAN with 21 or 23 characters is wrong before any arithmetic.
How do IBAN check digits work?
The two check digits are chosen so that the whole IBAN, rearranged and turned into a number, leaves a remainder of exactly 1 when divided by 97.
The method is MOD 97-10 from the ISO/IEC 7064 standard. Letters become two-digit numbers, A as 10 through Z as 35, so the arithmetic runs on a long string of digits.
Rearranged IBAN as a number, divided by 97, leaves a remainder of 1
Because 97 is a prime that shares no factor with any power of 10, replacing one digit with another, or one letter with another, or swapping two neighboring digits, always moves the remainder away from 1. To see how that holds up in practice, we generated 5,000 random IBANs in the British and German formats and tried every such single-character substitution, 1,056,928 variants: every one failed the test. Of 86,419 swaps of neighboring characters, 32 slipped through, and each swapped the last letter of a British bank code with the digit after it, which a format check rejects anyway because that position must be a letter.
Typing a letter where a digit belongs, or the reverse, is the weak spot: in a second run of 1,464,000 such typos, 14,832, about 1%, still left a remainder of 1. The fixed layout catches them wherever a position must hold a digit or a letter, which covers every position in British and German IBANs but not countries whose account part mixes both, such as Switzerland or Pakistan.
How do you verify an IBAN by hand?
Move the first four characters to the end, turn letters into numbers, then divide by 97 in chunks; a final remainder of 1 means the IBAN is valid.
Remove spaces and count
Write the IBAN without spaces and count the characters. GB29NWBK60161331926819 has 22, the British length, so it passes the first test.
Move the first four characters to the end
GB29 goes to the back, giving NWBK60161331926819GB29.
Replace letters with numbers
Use A = 10, B = 11 and so on up to Z = 35. N is 23, W is 32, B is 11, K is 20 and G is 16, which gives the 28-digit number 2332112060161331926819161129.
Divide by 97 in chunks
Most calculators cannot hold 28 digits, so take the first 9, find the remainder after dividing by 97, write that remainder in front of the next 7 digits and repeat until none are left.
Read the final remainder
A remainder of 1 means the IBAN is well formed. Anything else means at least one character is wrong, so ask the recipient to resend it rather than guessing which.
Worked example: Checking GB29 NWBK 6016 1331 9268 19 by hand
Working on the rearranged number 2332112060161331926819161129:
| Number to divide | Largest multiple of 97 below it | Remainder |
|---|---|---|
| 233211206 | 97 × 2,404,239 = 233,211,183 | 23 |
| 23 then 0161331, so 230161331 | 97 × 2,372,797 = 230,161,309 | 22 |
| 22 then 9268191, so 229268191 | 97 × 2,363,589 = 229,268,133 | 58 |
| 58 then 61129, so 5861129 | 97 × 60,424 = 5,861,128 | 1 |
The final remainder is 1, so the IBAN is valid. Swap its last two digits, to GB29 NWBK 6016 1331 9268 91, and the same steps end with a remainder of 5: the typo is caught before any money moves.
The same arithmetic produces check digits for a new IBAN, which shows why valid check digits alone prove so little.
Worked example: Working out the check digits of a German IBAN
A German BBAN is an 8-digit bank code followed by a 10-digit account number. Take the registry's example BBAN, 370400440532013000:
- Append the country code and 00: 370400440532013000DE00.
- Convert D to 13 and E to 14: 370400440532013000131400.
- Divide in chunks: 370400440 leaves 23; 235320130 leaves 70; 700013140 leaves 30; 300 leaves 9.
- Subtract from 98: 98 − 9 = 89.
The result, DE89 3704 0044 0532 0130 00, matches the registry's published example. Anyone can compute valid check digits for any account number, real or not.
What does a valid IBAN not prove?
A valid IBAN proves only that the code is well formed, not that the account is open or belongs to the person you mean to pay.
- Closed or wrong accounts. An IBAN copied from an old invoice still passes the test. The receiving bank returns the payment when it finds the account closed, usually minus fees and often days later.
- Name mismatches. Many banks credit by IBAN alone. Under EU Regulation 2024/886, euro-area banks have had to compare the name you type with the holder of the account behind the IBAN, before you authorize a euro transfer, since October 9, 2025, and banks in other EU countries must follow by July 9, 2027; the SEPA transfers guide covers how that check works. Outside the EU, a wrong name may not stop a payment.
- Fraudulent replacements. Criminals who take over an email thread send a new IBAN that is perfectly valid, because it belongs to an account they control. Confirm any change on a phone number you already have, and see money transfer scams for other warning signs.
Does the United States use IBANs?
US banks do not issue IBANs; the United States has no IBAN format, so a US account is identified by its routing number and account number.
What to send a payer in an IBAN country
- Your full name as the bank holds it, and your address
- Your account number
- Your bank's 9-digit routing number for incoming wires, which may differ from the one on your checks
- Your bank's SWIFT code, or the intermediary bank's code if your bank uses one
- Your bank's name and address
If the payer's form insists on an IBAN, the payer should ask their own bank how to enter a US account number rather than inventing one. Websites that claim to generate a US IBAN produce codes with no meaning, because there is no US format to follow. Which routing number to give is explained in routing number vs SWIFT code, and fees and exchange rates on arrival in receiving money from abroad in the US.
Worked example: A company in Madrid paying a US freelancer €2,500
The company pays from a Spanish IBAN with the registry's example layout, ES91 2100 0418 4502 0005 1332, 24 characters. The freelancer sends back her name and address, her made-up account number 4471 0098 2235, her bank's 9-digit wire routing number and its SWIFT code. The US is outside SEPA, so the Spanish bank sends a SWIFT wire rather than a SEPA transfer, and one of the banks converts the euros. At an assumed rate of 1.15 dollars per euro, chosen only for the arithmetic, €2,500 becomes $2,875 before fees; the EUR to USD converter shows the live mid-market rate.
Do you need a BIC as well as an IBAN?
For euro transfers within the EU, usually not, since banks may not demand one; for a SWIFT wire, including any payment from the US, expect to give both.
EU Regulation 260/2012 has barred banks from making customers supply a BIC for domestic euro transfers since February 1, 2014, and for cross-border euro transfers since February 1, 2016. The bank identifier inside the IBAN lets the bank find the BIC itself.
Outside that setting the BIC is still routine. A wire from a US bank to an IBAN in the UAE, Saudi Arabia, Pakistan or Turkey travels over SWIFT, and the sending bank needs the receiving bank's BIC to address the message. Some banks look it up from the IBAN for you and others make you type it; a BIC whose country letters differ from the IBAN's is worth questioning. Charges on those wires, including intermediary deductions, are set out in international wire transfer fees, and typical delivery times in how long international transfers take.
What are the most common IBAN mistakes?
Most rejected IBAN payments come down to a handful of slips: confused characters, a wrong length, a stale account or a fraudster's replacement.
- Look-alike characters. The letter O for zero, or a lowercase L for one, creeps in from handwriting and scanned invoices. Layouts are fixed, so in a British IBAN the only letters after the GB are characters 5 to 8.
- Printed spacing in an electronic field. Online forms and payment files want the code without spaces; pasting the groups of four can split it or add characters.
- A dropped or extra digit. The length changes, and the bank rejects the payment at once. Check the count against the table above.
- Old IBANs. Mergers and closed accounts leave valid-looking IBANs that no longer reach anyone.
- Doubting a Portuguese IBAN. Banco de Portugal notes that Portuguese IBANs always have 50 as their check digits; that is correct, not a typo.
- Swapped fields. An IBAN in the BIC field, or the reverse, fails validation. A BIC has 8 or 11 characters and never carries check digits.
Before sending, compare what the recipient will actually receive with the money transfer cost calculator, and check the mid-market rate on the USD to EUR converter.