IBAN Validator

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uk iban validator

UK IBAN Validator

UK IBANs start with GB and have 22 characters. The UK is not part of the eurozone, but it registered an IBAN format to receive international and SEPA transfers.

The UK IBAN format

The UK's IBAN has 22 characters: GB, then 2 check digits, then an 18-character BBAN, the first 4 characters are letters (the bank's BIC code, e.g. BUKB for Barclays), followed by a 6-digit sort code and an 8-digit account number.
Domestically, UK banks and customers still use the sort code (6 digits) and account number (8 digits) separately for everyday banking; the IBAN only comes into play for international and SEPA transfers, since the domestic Faster Payments system doesn't require it.
The UK IBAN's check digit follows the same ISO 7064 rule (mod 97-10): the first 4 characters of the provisional IBAN (GB00...) move to the end, each BBAN letter becomes two digits (A=10 through Z=35, including the 4 bank-code letters), and the resulting number must leave a remainder of 1 when divided by 97. Because the UK BBAN starts with letters, it produces the biggest digit expansion among this series' 5 countries: 4 letters become 8 digits before the remaining 14 numeric digits (sort code plus account) even enter the sum.
The 6-digit sort code has been administered since 1957 by the committee that today operates as part of Pay.UK, the body behind Britain's domestic payment systems (Bacs, Faster Payments and Cheque and Credit). The UK never joined the euro, but it takes part in SEPA for euro transfers received from abroad, which is why it has an IBAN format at all despite not using the shared currency.

Examples

Valid UK IBAN

Input: GB33BUKB20201555555555
Expected output: Valid

Classic example cited in banking documentation (Barclays), 22 characters.

Invalid BBAN characters

Input: GB33-BUKB-2020-1555-5555-55
Expected output: Invalid characters

Hyphens are not valid IBAN characters, only spaces are stripped during normalization.

Two digits missing

Input: GB33BUKB202015555555
Expected output: Wrong length

20 characters instead of 22: the account number is missing its final 2 digits, so the validator rejects it before even computing the mod-97 check.

Full tool FAQ

What does it mean when an IBAN is 'valid'?

It means the IBAN has the correct length for its country and its check digits satisfy the ISO 7064 MOD97-10 checksum defined by ISO 13616. It confirms the number is well-formed and free of typos, it does not confirm that the underlying bank account actually exists or is open, only the account-holding bank can verify that.

Why did my IBAN come back as 'wrong length'?

Why did it say the country code is unknown?

Can two different IBANs have the same check digits?

Does a valid checksum guarantee the account exists?

Why does the BBAN show as one long string instead of bank code and account number?

Is this the same as a SWIFT/BIC code?

Why do some countries not use IBAN at all?

Frequently asked questions

Does the UK use IBAN even outside the eurozone?

Yes. The UK registered an IBAN format (GB, 22 characters) to take part in international and SEPA transfers, even without using the euro as its currency.

Are sort code and IBAN the same thing?

No. The sort code (6 digits) identifies the bank and branch for domestic use; it's embedded inside the IBAN's BBAN, but for payments within the UK usually only the sort code and account number are used.

Why does the UK BBAN start with letters?

The first 4 characters of the UK BBAN are the bank's BIC code (for example BUKB for Barclays), unlike most European countries, which use purely numeric bank codes.

Why does the UK have an IBAN if it doesn't use the euro?

Because it takes part in SEPA to receive international euro transfers; the UK's IBAN (GB, 22 characters) was registered for that purpose, while domestic sterling payments still use sort code and account number via Bacs or Faster Payments.

Next steps

The UK IBAN format

The UK's IBAN has 22 characters: GB, then 2 check digits, then an 18-character BBAN, the first 4 characters are letters (the bank's BIC code, e.g. BUKB for Barclays), followed by a 6-digit sort code and an 8-digit account number.

Domestically, UK banks and customers still use the sort code (6 digits) and account number (8 digits) separately for everyday banking; the IBAN only comes into play for international and SEPA transfers, since the domestic Faster Payments system doesn't require it.

The UK IBAN's check digit follows the same ISO 7064 rule (mod 97-10): the first 4 characters of the provisional IBAN (GB00...) move to the end, each BBAN letter becomes two digits (A=10 through Z=35, including the 4 bank-code letters), and the resulting number must leave a remainder of 1 when divided by 97. Because the UK BBAN starts with letters, it produces the biggest digit expansion among this series' 5 countries: 4 letters become 8 digits before the remaining 14 numeric digits (sort code plus account) even enter the sum.

The 6-digit sort code has been administered since 1957 by the committee that today operates as part of Pay.UK, the body behind Britain's domestic payment systems (Bacs, Faster Payments and Cheque and Credit). The UK never joined the euro, but it takes part in SEPA for euro transfers received from abroad, which is why it has an IBAN format at all despite not using the shared currency.

Examples

Valid UK IBAN

Input: GB33BUKB20201555555555
Expected output: Valid

Classic example cited in banking documentation (Barclays), 22 characters.

Invalid BBAN characters

Input: GB33-BUKB-2020-1555-5555-55
Expected output: Invalid characters

Hyphens are not valid IBAN characters, only spaces are stripped during normalization.

Two digits missing

Input: GB33BUKB202015555555
Expected output: Wrong length

20 characters instead of 22: the account number is missing its final 2 digits, so the validator rejects it before even computing the mod-97 check.

Full tool FAQ

What does it mean when an IBAN is 'valid'?

Why did my IBAN come back as 'wrong length'?

Why did it say the country code is unknown?

Can two different IBANs have the same check digits?

Does a valid checksum guarantee the account exists?

Why does the BBAN show as one long string instead of bank code and account number?

Is this the same as a SWIFT/BIC code?

Why do some countries not use IBAN at all?

Frequently asked questions

Does the UK use IBAN even outside the eurozone?

Yes. The UK registered an IBAN format (GB, 22 characters) to take part in international and SEPA transfers, even without using the euro as its currency.

Are sort code and IBAN the same thing?

Why does the UK BBAN start with letters?

The first 4 characters of the UK BBAN are the bank's BIC code (for example BUKB for Barclays), unlike most European countries, which use purely numeric bank codes.