IBAN, SWIFT & International Payments
How to Check an IBAN: Format, Check Digits and Common Errors
An IBAN (International Bank Account Number) identifies one specific bank account in a format that banks in more than 80 countries understand. If even one character is wrong, a transfer can be rejected, delayed for days, or in the worst case land in somebody else's account.
The good news is that every IBAN carries its own built-in error check. This guide shows how that check works, what it can and cannot prove, and the short routine to follow before you send money abroad.
Key takeaways
- An IBAN has up to 34 characters: a 2-letter country code, 2 check digits, then the domestic account details (the BBAN).
- The check digits use the ISO 7064 mod-97 method, which catches virtually every single-character typo and swapped pair.
- A valid IBAN only proves the number is well-formed. It does not prove the account exists or belongs to the person you are paying.
- For euro transfers in the EU, banks now run Verification of Payee, which compares the IBAN with the recipient's name.
The anatomy of an IBAN
IBANs are defined by the international standard ISO 13616, and SWIFT maintains the official registry of national formats. Every IBAN follows the same three-part pattern:
| Part | Length | Example (DE89 3704 0044 0532 0130 00) | What it means |
|---|---|---|---|
| Country code | 2 letters | DE | Germany (ISO 3166 code) |
| Check digits | 2 digits | 89 | Calculated from the rest of the IBAN |
| BBAN | Varies by country | 3704 0044 0532 0130 00 | Bank code 37040044 + account number 0532013000 |
The BBAN (Basic Bank Account Number) is simply the domestic account number in a fixed layout. In Germany it contains the 8-digit bank code (Bankleitzahl) and a 10-digit account number; in the UK it contains a 4-letter bank code, the 6-digit sort code and an 8-digit account number. Because each country fixes its own length, the length alone is the first and easiest test. See the full list in our IBAN format by country guide.
IBANs are usually printed in groups of four for readability. The spaces are not part of the number, and upper or lower case does not matter.
How the check digits work, step by step
The two check digits are produced with the ISO 7064 mod-97 algorithm. You can reproduce the check yourself with the well-known example IBAN GB82 WEST 1234 5698 7654 32:
- Remove the spaces: GB82WEST12345698765432
- Move the first four characters to the end: WEST12345698765432GB82
- Replace every letter with two digits, where A = 10, B = 11 … Z = 35. W = 32, E = 14, S = 28, T = 29, G = 16, B = 11.
- You now have one long number: 3214282912345698765432161182
- Divide that number by 97. If the remainder is exactly 1, the IBAN passes.
Change the final digit from 2 to 3 and the remainder becomes 28. Swap the last two digits and it becomes 49. Either way the IBAN fails, which is why a checker can flag a typo before your bank ever sees it.
Why 97?
97 is the largest two-digit prime number. Using a prime makes the remainder sensitive to almost every kind of small mistake, including the two most common human errors: a single wrong character and two neighbouring characters typed in the wrong order.
Paste any IBAN into the free FloatForex IBAN checker to test its length, country format and check digits instantly.
Validate an IBANWhat a valid IBAN cannot tell you
Passing the mod-97 test is necessary, but it is not proof that your payment will reach the right person. A structurally valid IBAN can still be:
- An account that has been closed or never opened.
- A real account that belongs to someone else, for example when an invoice has been tampered with in an email-fraud scam.
- Correct for the country but for a bank that cannot receive the currency you are sending.
This is why the EU's Instant Payments Regulation requires banks to offer Verification of Payee for euro credit transfers from 9 October 2025: before you confirm, your bank checks that the IBAN matches the recipient name you entered and warns you if it does not. The UK has a similar service called Confirmation of Payee. Treat a mismatch warning seriously, especially if the bank details arrived by email.
Changed bank details? Call first.
If a supplier, landlord or relative suddenly sends new bank details, confirm them by phone on a number you already know. A perfectly valid IBAN is exactly what a fraudster will send you.
The most common IBAN errors
| Error | Typical cause | How to spot it |
|---|---|---|
| Wrong length | A digit dropped or added while copying | Compare with the country's fixed length |
| Letter O instead of zero (or I instead of 1) | Reading from a paper invoice or photo | Check digits fail; the BBAN of most countries is all digits |
| Check digits fail | Any single typo or swapped pair | Run the IBAN through a validator |
| Country does not use IBAN | Paying the US, Canada, Australia, China or India | Ask for the local account number plus SWIFT/BIC instead |
| SWIFT/BIC entered in the IBAN field | The two codes look similar on bank letters | A BIC has 8 or 11 characters and no check digits |
Not sure which code goes where? Our IBAN vs SWIFT/BIC guide explains when you need one, the other, or both.
A 5-step checklist before every transfer
- Copy the IBAN electronically instead of retyping it whenever you can.
- Run it through the IBAN validator to confirm length, country format and check digits.
- Confirm the recipient name exactly as the bank holds it, and read any Verification or Confirmation of Payee result.
- For payments outside the euro area, add the bank's SWIFT/BIC code and confirm the currency the account receives.
- For first-time or unusually large payments, send a small test amount first.
Frequently asked questions
Is an IBAN the same as my account number?
No. Your domestic account number is contained inside the IBAN, but the IBAN adds a country code, two check digits and usually a bank or branch code, so it identifies the account internationally.
Can an IBAN be valid but still wrong?
Yes. The check digits only prove that the number is internally consistent. It can still belong to a closed account or to the wrong person, which is why the recipient's name should be checked too.
Is it safe to share my IBAN?
Generally yes. People need your IBAN to pay you, and it cannot be used on its own to withdraw money. Be cautious about direct-debit mandates you did not authorise and check your statements regularly.
Does the US use IBANs?
No. US accounts are identified by an account number and a 9-digit ABA routing number. International payments to the US normally use the account number plus the bank's SWIFT/BIC code.
Sources
This guide is general educational information, not financial, tax or legal advice. Figures were checked on the date shown and can change. Read how we research and review content in our editorial standards. Source: https://www.floatforex.com/guides/how-to-check-an-iban