Free tool · Check bank details
UK IBAN checker
Check that an IBAN is correctly formed: the country, its length and the check digits. For UK IBANs we also split out the sort code and account number and run the official modulus check. Everything runs in your browser.
We deliberately don't name the bank behind a bank code, or turn a sort code and account number into an IBAN: both need licensed data.
What's inside an IBAN
An IBAN (International Bank Account Number) is a standard wrapper around a country's own account number. It always starts the same way: a two-letter country code, then two check digits. The rest is the domestic account number, called the BBAN, laid out the way that country's banks define it. Each country's IBAN has a fixed length, recorded in the official IBAN registry, from 15 characters in Norway to 32 in Saint Lucia.
A UK IBAN is always 22 characters, for example GB29 NWBK 6016 1331 9268 19. After GB and the check digits come a four-letter bank code (NWBK), the six-digit sort code (60-16-13) and the eight-digit account number (31926819). Accounts in Jersey, Guernsey and the Isle of Man use the same GB format.
What this checker tests
- The country code is one that issues IBANs, and the IBAN is the right length for that country.
- The characters after the check digits match the country's format, such as digits only where the country only uses digits.
- The two check digits are right. They're calculated from the whole IBAN using the ISO 13616 mod-97 method, which catches any single wrong character and any two neighbouring characters swapped round.
- For UK IBANs, the sort code and account number also pass the Vocalink modulus check, the same check our sort code checker runs.
You can paste an IBAN with spaces, in lower case, or with "IBAN" in front of it. We tidy it up and show it in groups of four, the way it's usually printed.
Why a UK IBAN can pass and still be wrong
The check digits only prove the IBAN was copied correctly from wherever it came from. Someone can calculate valid check digits for any sort code and account number, real or not. That's why we also run the modulus check on UK IBANs. An IBAN with correct check digits but an account number that fails the modulus check was put together wrongly, and shouldn't be paid.
What we deliberately don't do
We don't convert a sort code and account number into an IBAN, and we don't show which bank a bank code belongs to. Getting the bank code right needs the industry's licensed sort code and BIC data. A guess risks giving you an IBAN that looks right but points somewhere else, and that's worse than no answer. If you need a supplier's IBAN, ask them for it, or use the IBAN shown on their bank statement or in their banking app.
Correct format isn't the same as verified
A valid IBAN tells you the number is well formed. It doesn't tell you whose account it is. In invoice fraud the bank details are real and correctly formed: they just belong to the fraudster. For UK payments, Confirmation of Payee in your banking app checks the name on the account. Paylist goes further. Businesses list their bank details once, we verify them, and you look them up with a Paylist number instead of trusting an email. Paylist doesn't move money. It's how you check before you pay.
Privacy
The check runs entirely in your browser. The IBAN you enter isn't sent to Paylist or anyone else, and isn't stored. We count how often the tool is used and whether the IBAN passed, never the IBAN itself.
Frequently asked questions
How do I know if an IBAN is valid?
Paste it into the checker. A valid IBAN has a recognised country code, the right length for that country, the right format, and check digits that pass the mod-97 calculation. UK IBANs also need the sort code and account number to pass the modulus check.
How long is a UK IBAN?
22 characters: GB, two check digits, a four-letter bank code, a six-digit sort code and an eight-digit account number. For example, GB29 NWBK 6016 1331 9268 19.
Can you work out my IBAN from my sort code and account number?
We don't, on purpose. The four-letter bank code comes from licensed industry data, and a wrong guess would produce an IBAN that looks valid but isn't yours. Your bank shows your IBAN on statements and in its app.
Does a valid IBAN mean the account exists?
No. It means the IBAN is correctly formed. It doesn't tell you whether the account is open or who owns it. For UK accounts, Confirmation of Payee checks the name; a verified Paylist listing tells you the details belong to the business.
Which bank does this IBAN belong to?
We show the bank code from a UK IBAN, but we don't look up which bank it belongs to. That mapping comes from licensed sort code and BIC data, which this free tool doesn't use.
Do Jersey, Guernsey and Isle of Man IBANs work?
Yes. They use the UK's GB format, so they're checked exactly like any other UK IBAN, including the modulus check.
Is the IBAN I enter sent anywhere?
No. The check runs in your browser. We record that the tool was used and whether the IBAN passed, but never the IBAN itself.
Check before you pay — every time
Paylist is a verified directory of UK business bank details. Your suppliers list theirs once, and you look them up instead of trusting an email.