In this article
An IBAN, or International Bank Account Number, is a bank account number written in one international format defined by the standard ISO 13616: a two-letter country code, two check digits, and then the domestic account details of that country, up to 34 characters in all. It identifies one account at one bank, and its check digits let anyone, with a pencil or a spreadsheet, detect most typing errors before a payment is sent.
An IBAN is not a new account. It is the existing domestic account number, with the bank and branch codes that country already uses, wrapped in a prefix that says which country's format to read and whether the string has been copied correctly. An IBAN that passes every check can still belong to someone other than the person you meant to pay.
The rules quoted below come from SWIFT's IBAN registry, the European Union's regulation on credit transfers and direct debits in euro, and the amendments made to it by the Union's instant payments regulation. The parts on European law are general information, not legal advice.
Counts computed on the fictional example IBAN used in this article; the method is the modulo 97 check named in the IBAN registry.
What is an IBAN made of?
An IBAN is made of three parts in a fixed order: a two-letter country code, two check digits, and the basic bank account number, called the BBAN, which holds the domestic bank, branch and account details. SWIFT's IBAN registry describes the BBAN as up to thirty alphanumeric characters, so the longest possible IBAN has 2 + 2 + 30 = 34 characters.
The country code comes from the ISO 3166 list of country codes. It tells the reader which national format applies to everything that follows.
The two check digits are computed from all the other characters. They carry no information about the bank or the holder: their only purpose is to make a miscopied IBAN fail an arithmetic test.
The BBAN is the national part, and each country decides its content. The registry records each national format in a compact notation. The United Kingdom's BBAN, for instance, is registered as four letters identifying the bank, six digits for the branch, which is the sort code, and eight digits for the account number: 18 characters, which with the four-character prefix gives a 22-character IBAN. Germany's is an eight-digit bank code followed by a ten-digit account number, also 18 characters. France's runs to 23 characters: a five-digit bank code, a five-digit branch code, an eleven-character account number that may contain letters, and a two-digit national key.
Two properties of the BBAN matter in practice. Its length is fixed for each country, so every IBAN of a given country has the same number of characters. And the bank identifier sits at a fixed position inside it, which is how a paying bank can work out the receiving bank from the IBAN alone.
Who defines the IBAN and who keeps the list of formats?
The IBAN is defined by the international standard ISO 13616, and SWIFT keeps the official list of national formats as the registration authority designated by ISO. SWIFT states that the standard specifies the structure of a compliant national IBAN format, and that only a national standards body or a national central bank may ask for a country's format to be registered.
The list is called the IBAN registry. For each country it gives the BBAN structure, the BBAN length, the IBAN length, the position of the bank identifier, whether the country belongs to the Single Euro Payments Area, and one example shown in both written forms. The release read for this article is number 103, dated September 2026, and its table of contents lists 89 national formats.
Nothing in this arrangement makes SWIFT the issuer of your IBAN. Your bank builds it from your account details according to the national format, and the registry only publishes what that format is. Some countries add national keys or padding rules that are easy to get wrong, so the reliable IBAN of an account is the one printed on its statement.
How long is an IBAN, and why does the length change by country?
An IBAN is at most 34 characters long, and its actual length is fixed country by country because each country keeps its own domestic account format inside it. In the national formats read in SWIFT's IBAN registry for this article, the length runs from 15 characters for Norway to 33 for the Russian Federation.
Lengths as registered in SWIFT's IBAN registry, release 103 (September 2026). A selection of eleven formats, not the whole registry.
The length is a first filter. Count the characters before doing anything else: a German IBAN with 21 or 23 characters is wrong whatever its check digits say, and no arithmetic is needed to know it. A payment form built for one country's length will also cut off another country's IBAN.
How do you check an IBAN by hand?
To check an IBAN by hand, move its first four characters to the end, replace every letter by a two-digit number (A is 10, B is 11, and so on to Z, 35), and divide the resulting number by 97: the IBAN is well formed only if the remainder is exactly 1. SWIFT's IBAN registry names this method as the modulo 97 scheme of the standard ISO 7064.
The example below is fictional and built for this article. It uses the country code XX, which is assigned to no country, and an invented 18-character format: the prefix, a four-letter bank code DEMO, and a ten-digit account number. No such account can exist. The example IBAN is XX66 DEMO 0012 3456 78.
The number produced by the conversion is far too long for a pocket calculator, so the division is done in pieces. The remainder of each piece is carried in front of the next digits, and the result is the same as dividing the whole number in one go.
- Remove the spaces and countThe string is XX66DEMO0012345678, which has 18 characters, the length of the invented format. A real IBAN is compared with its country's registered length at this point.
- Move the first four characters to the endXX66 goes behind the account details, giving DEMO0012345678XX66.
- Replace each letter by its numberDEMO becomes 13 14 22 24 and XX becomes 33 33. Written without gaps, the number to divide is 131422240012345678333366, which has 24 digits.
- Divide the first nine digits by 97131422240 divided by 97 leaves a remainder of 44.
- Carry the remainder into the next digitsPut 44 in front of the next seven digits, 0123456, to make 440123456. Divided by 97, it leaves 21.
- RepeatPut 21 in front of the next seven digits, 7833336, to make 217833336. Divided by 97, it leaves 48.
- Finish with the last digitPut 48 in front of the one digit left, 6, to make 486. Since 97 times 5 is 485, the remainder is 1: the string is a well-formed IBAN. Any other remainder means at least one character is wrong.
On a calculator, the remainder of each step is found by dividing, dropping the decimals, multiplying that whole number by 97 and subtracting.
How are the two check digits calculated in the first place?
The two check digits are calculated by the bank with the same arithmetic run in reverse: the check digits are set to 00, the remainder of the division by 97 is taken, and that remainder is subtracted from 98. On the fictional example, the remainder is 32 and 98 minus 32 gives the check digits 66.
Start from the account details and the country code with 00 in place of the check digits: DEMO0012345678XX00. Converted to digits, this is 131422240012345678333300. The first two pieces are the same as in the validation above and leave 44, then 21. The third piece is 217833330, which leaves 42. The last piece is 420, which leaves 32. The check digits are 98 minus 32, that is 66, and a result under 10 would be written with a leading zero.
This is why the check digits cannot be guessed from a neighbouring account. An account number ending in 87 instead of 78, with everything else unchanged, has the check digits 17, not 66.
What does the check catch, and what does it miss?
The modulo 97 check catches the ordinary copying errors, a wrong character or two neighbouring characters swapped, and it misses everything that is not a copying error: a well-formed IBAN says nothing about who holds the account, whether the account is open, or whether it is the account you were meant to pay.
The table applies the check to variations of the fictional example.
| Variation of the example | What was tested | Result |
|---|---|---|
| Last digit typed 9 instead of 8 | XX66 DEMO 0012 3456 79 | Remainder 28: rejected |
| Two digits swapped, 45 typed as 54 | XX66 DEMO 0012 3546 78 | Remainder 16: rejected |
| Any one character replaced by another of the same kind | 258 possible slips | 0 pass |
| Any two neighbouring characters swapped | 14 possible swaps | 0 pass |
| Any two digits of the account number wrong at once | 3,645 possible slips | 25 pass |
When two digits are wrong at the same time, a small share of the errors cancel each other out: on this example, 25 of the 3,645 combinations, about 0.7%. One of them is XX66 DEMO 6012 3456 68, where the first digit of the account number and the second to last are both wrong, and the remainder is still 1. More generally, a string of the right length that has nothing to do with the original has about one chance in 97 of passing, a little over 1%.
The check is therefore a filter for honest slips, not a control on identity. A fraudulent change of bank details on an invoice always supplies a perfectly valid IBAN, because the account behind it really exists. Confirming new or changed bank details through a contact you already hold on file, rather than through the message that announced the change, is the control that addresses that risk.
How is an IBAN different from a BIC, a routing number, a sort code and an account number?
An IBAN identifies one account, a BIC identifies an institution, and routing numbers and sort codes identify a bank or branch inside one country's domestic system; an account number alone identifies an account only within its own bank. The IBAN is the only one of these that combines the country, the bank and the account in a single string with a built-in check.
| Identifier | What it identifies | Form | Where it is used |
|---|---|---|---|
| IBAN | One account, with its country and bank | Up to 34 characters, fixed length per country | Countries with a registered format |
| BIC | An institution, optionally a branch | 8 characters, or 11 with the branch code | International payment messages |
| Sort code | A bank branch | 6 digits | United Kingdom domestic payments |
| Routing number | A financial institution | 9 digits | United States domestic payments |
| Account number | An account within one bank | Set by the bank or the country | Domestic payments, alongside a bank code |
The BIC, or business identifier code, is defined by the standard ISO 9362, and SWIFT issues the codes as registration authority. SWIFT describes it as an eight-character code made of a four-character business party prefix, a two-letter country code and a two-character suffix, to which an optional three-character branch identifier may be added. It is often called a SWIFT code in everyday use.
The sort code is already inside a United Kingdom IBAN: it is the six digits registered as the branch identifier, followed by the eight-digit account number. In the United States, the American Bankers Association describes the routing number as a nine-digit number issued only to federally or state chartered financial institutions, and a payment needs it together with the account number.
When a payment leaves the IBAN area, the two systems are combined rather than converted. A transfer to a United States account is typically instructed with the account number, the routing number or the bank's BIC, and the beneficiary's name and address; there is no IBAN to supply.
Which countries use IBANs, and which do not?
IBANs are used by the countries that have registered a national format with SWIFT, which covers the European Union, its neighbours in the Single Euro Payments Area and a number of countries in the Middle East, North Africa, Central Asia, Latin America and the Caribbean; the United States, Canada and Australia are not among them. None of those three appears in the country list of SWIFT's IBAN registry, release 103.
Banks in those countries do not issue IBANs. Payments to those countries use the domestic identifiers, the account number together with the routing number in the United States, with the institution and branch transit numbers in Canada, and with the branch code known as the BSB in Australia, usually accompanied by the bank's BIC on an international transfer.
Use is not uniform among the countries that do have a format. In the European Union the IBAN is the mandatory account identifier for credit transfers and direct debits in euro. Elsewhere a country may have registered a format while its banks still accept domestic numbers for local payments: the registry tells you the format, and the receiving bank tells you what it requires.
What does European law say about IBANs and BICs?
European Union law makes the IBAN the account identifier for credit transfers and direct debits in euro, forbids banks to ask a payer for the BIC, and forbids payers and payees to refuse an account because of the Member State where it is held. All three rules are in Regulation (EU) No 260/2012, the regulation that set the technical requirements for the Single Euro Payments Area.
The first rule is in the regulation's annex, which states that the payment account identifier must be the IBAN, and in Article 5, which requires payment service providers to use it whatever the location of the providers concerned.
The second is Article 5(7): after 1 February 2014 for national payments and after 1 February 2016 for cross-border payments, payment service providers shall not require users to indicate the BIC of the payer's or the payee's provider. The bank derives the receiving institution from the bank identifier inside the IBAN. A BIC is still commonly requested for transfers the regulation does not cover.
The third is Article 9. A payer making a credit transfer to an account within the Union shall not specify the Member State in which that account is to be located, and a payee collecting by direct debit is under the same prohibition for the payer's account, provided the account is reachable. Refusing an IBAN of another Member State in these cases is widely called IBAN discrimination.
Article 9 speaks of Member States, so the obligation it creates concerns accounts held in the Union. The payment area itself is wider than the Union, and the registry marks which national formats belong to it, the United Kingdom's among them. Whether a party is legally bound to accept an IBAN from a participating country outside the Union depends on the law that applies to that party, not on the format of the number.
What is verification of payee, and when did it start?
Verification of payee is a service in which the payer's bank checks, before the payer authorises a credit transfer, whether the name the payer entered matches the name held for that IBAN at the payee's bank. The European Union's instant payments regulation, Regulation (EU) 2024/886, wrote the service into Regulation 260/2012 as Article 5c, and payment service providers in euro area Member States had to comply by 9 October 2025.
Providers located in Member States whose currency is not the euro have until 9 July 2027. The article covers credit transfers in euro generally, not only instant ones, and the regulation requires the service to be provided to all users free of charge.
The mechanism closes the gap the check digits leave open:
- The check runs immediately after the payer gives the payee's details and before the payer is offered the possibility of authorising the transfer.
- Where the name and the IBAN do not match, the payer's provider notifies the payer of it, on the basis of information from the payee's provider.
- Where they almost match, the payer's provider indicates to the payer the name associated with the IBAN.
- With any such notification, the provider must tell the payer that authorising the transfer might lead to the funds going to an account not held by the payee the payer indicated.
- Users that are not consumers must be given the means to opt out when they submit multiple payment orders as a package, and may opt back in at any time.
The payer still decides after a notice. A provider that complied with the article is not held liable for a transfer made to an unintended payee on the basis of an incorrect identifier, while a payer's provider that failed to comply must refund the payer where that failure led to a defectively executed transaction.
Two practical points follow for a business. If you are paid by transfer, the name on your invoice should be the name your bank holds for the account, since a trading name that differs from it can produce a mismatch notice at your customer's bank. And if you pay suppliers in batches with the check switched off, the verification of new or changed bank details has to happen in your own process.
How is an IBAN written on paper and in a file?
An IBAN has two written forms: the print format, in groups of four characters separated by spaces with a shorter last group if needed, and the electronic format, the same characters as one continuous string. SWIFT's IBAN registry shows both forms for every country's example.
Groups of four make it possible to compare a number on screen with a number on paper group by group. The electronic format is what a payment file, a database field or an online banking form stores.
The spaces are not part of the IBAN: a system that receives a pasted IBAN should strip the spaces and convert lower case to upper case before it checks the length and the remainder; a document meant for people should show the grouped form.
What goes wrong most often with an IBAN?
The errors that occur with an IBAN fall into two groups: copying and format errors, which the length count and the modulo 97 check catch, and errors of substance, where a well-formed IBAN is out of date or belongs to the wrong party, which no format check can see. The first four below belong to the first group, the last two to the second.
- Wrong length. A character dropped or doubled while retyping.
- Look-alike characters. The letter O for the digit 0, the letter I for the digit 1.
- A domestic number in the IBAN field. A sort code and account number, or a routing number and account number, typed where an IBAN is asked for.
- An IBAN invented for a country that has none. A prefix added to an American, Canadian or Australian account number.
- An outdated IBAN. An account closed or moved to another bank. The number remains well formed.
- The right format, the wrong party. Details copied from another supplier's record, or replaced by a third party's. The check digits pass; this is the case name checks and call-back controls are for.
When a transfer has already been sent to a well-formed but wrong IBAN, the format offers no remedy: the payment follows the number, not the name written beside it. Contact the paying bank at once.
How to follow a transfer once it has left and how to confirm that it arrived are separate subjects with their own procedures. So is what the banks between the two ends do with the payment, which is the business of the SWIFT network and of correspondent banks.
Where does the IBAN go on an invoice?
On an invoice, the IBAN belongs in the payment details block, next to the exact name of the account holder, the bank's name and BIC, the currency of the account and the payment reference you want the customer to quote. It is written in groups of four, in text that can be copied.
The account holder's name is the name the customer's bank will compare with the IBAN where a name check applies, so it should be written as the bank holds it.
A customer paying in euro inside the Union does not need the BIC, but a customer paying from outside, or in another currency, will usually be asked for it by their bank.
State the currency of the account, since an IBAN does not say which currency the account is held in.
If your account is in a country without IBANs, say so plainly in the payment block and give the domestic identifiers with their labels: account number, routing number or its local equivalent, bank name, BIC and bank address.
Last, say how changes will be announced. A line stating that any change of bank details will be confirmed through a named contact, never by an invoice alone, gives your customer's accounts payable team a rule to hold you to.
