CrispUtils

IBAN validator and decoder

Paste an IBAN to confirm its length and check digits are correct before you send a payment, and see how the number splits into bank, branch and account for the main European countries.

Spaces and punctuation are ignored. Nothing is sent anywhere.

Try an example
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An IBAN has a built-in error check. The two digits after the country code are a checksum calculated from everything else, using the mod-97 rule from ISO 13616. If a digit is mistyped or two are transposed, the checksum almost certainly fails — which is exactly what it exists to catch, since a payment sent to a valid-looking wrong account is very difficult to recover.

This validates the country code, the expected length for that country, and the check digits, then breaks the number into its parts. For Italy it separates CIN, ABI and CAB; for the UK the bank code and sort code; and similarly for Germany, France, Spain and the Netherlands.

It cannot tell you whether the account exists or who owns it — that needs a bank. It tells you whether the number itself is internally consistent, which catches the overwhelming majority of real typing errors.

How to use this tool

  1. Paste the IBAN. Spaces and punctuation are ignored, so you can paste it however it was written.
  2. Read the verdict. Valid means the country, length and check digits are all correct.
  3. If it fails, read the reason — wrong length for the country, an unknown country code, or a checksum mismatch meaning a typo.
  4. Check the breakdown against the bank details you were given; the bank and branch codes are a useful sanity check.
  5. Copy the number without spaces if you need to paste it into a banking form.

Worked example

Checking supplier details before paying

An invoice arrives with new bank details. The IBAN validates, and the breakdown shows an ABI code belonging to a different bank than the one named on the invoice. That is worth a phone call to a number you already have — invoice fraud usually works by changing exactly this.

Finding a transposition

A payment keeps being rejected. The IBAN is the right length but the checksum fails, so two digits have been swapped somewhere. Comparing against the original document finds it immediately.

Common use cases

  • Checking supplier bank details before a transfer
  • Validating an IBAN typed from a printed invoice
  • Confirming the length is right for the country
  • Splitting out the bank and branch codes to cross-check a bank name
  • Cleaning a list of account numbers before importing it
  • Checking your own IBAN before giving it to an employer

Common mistakes

  • Assuming valid means it exists — The checksum proves the number is internally consistent, not that an account is behind it. Only the bank can confirm that.
  • Trusting bank details that changed by email — Invoice redirection fraud almost always arrives as an email saying the account has changed. Always confirm by phone, using a number you already had.
  • Assuming every IBAN is the same length — They range from 15 characters in Norway to 32 in Saint Lucia. Length is country-specific, which is why a wrong-length number is rejected here.
  • Retyping instead of copying — Every manual retype is a chance to transpose two digits. Copy and paste, then validate.

Frequently asked questions

How does the check digit calculation work?

Move the first four characters to the end, convert every letter to a number (A=10 … Z=35), treat the result as one very large integer and divide by 97. A valid IBAN leaves a remainder of exactly 1. That single rule catches virtually all single-character errors and transpositions.

Does a valid IBAN mean the account exists?

No. It means the number is structurally correct and the check digits agree. Whether an account exists, and whose it is, can only be confirmed by a bank. Some banks offer a confirmation-of-payee check that compares the account holder's name.

Is my IBAN sent anywhere?

No. The mod-97 calculation and the country rules are in the page, so validation happens entirely in your browser. Nothing is transmitted or logged.

Why does my IBAN fail even though I copied it correctly?

Check for a missing or extra character at the start, a letter O typed instead of a zero, or a country code in lowercase. If the length is right and the checksum still fails, something in the middle differs from the original — compare digit by digit.

What are ABI and CAB on an Italian IBAN?

ABI is the five-digit bank code and CAB the five-digit branch code; the single letter before them is the CIN, a domestic check character predating the IBAN. Together they identify the specific branch holding the account.

Do I still need a BIC or SWIFT code?

Inside the SEPA area, usually not — the IBAN alone is enough for euro transfers. Outside SEPA, or for payments in other currencies, a BIC is often still required.

Last updated 2026-09-26