IBAN Validator & Formatter — 100% Offline

Catch a mistyped IBAN before a transfer fails, or before money reaches the wrong account. This Actor validates a batch of IBANs and returns each one cleanly formatted.

100% offline: no external call, no third-party lookup, nothing leaves the run. Pure arithmetic, no signup, no API key.

What it does

For every IBAN you send, it:

1. Normalises the input — strips spaces, upper-cases letters.
2. Checks the country code against the ISO 13616 registry (78 countries are covered) and confirms the IBAN has exactly the length that country uses. A German IBAN is 22 characters, a French one 27, a Norwegian one 15 — the wrong length is the most common paste error and it is caught here.
3. Verifies the mod-97 checksum: the first four characters are moved to the end, letters are converted to numbers (A=10 … Z=35), and the resulting very large number must leave a remainder of 1 when divided by 97. This is the check that catches single-digit typos and transposed digits.
4. Extracts the BBAN (the country-specific part after the check digits) and returns a human-readable version grouped in blocks of four.

Use cases

• Payments and payroll — sanity-check supplier or employee IBANs before a transfer run, rather than paying bank fees on a rejected transfer.
• Onboarding and KYC forms — give immediate feedback on a mistyped IBAN at the point of entry, before it becomes a failed payment weeks later.
• Finance data cleanup — bulk-check a column of IBANs pulled from a spreadsheet, a CRM export or a legacy ERP.
• Formatting for display — turn FR1420041010050500013M02606 into FR14 2004 1010 0505 0001 3M02 606 for a statement or a PDF.

Input

{
  "ibans": [
    "FR1420041010050500013M02606",
    "de89 3704 0044 0532 0130 00",
    "GB00WEST12345698765432"
  ]
}

Spaces and lower-case letters are fine — the input is normalised for you.

Output (one row per IBAN)

{
  "input": "FR1420041010050500013M02606",
  "iban_normalized": "FR1420041010050500013M02606",
  "valid_format": true,
  "valid_checksum": true,
  "country_code": "FR",
  "expected_length": 27,
  "actual_length": 27,
  "bban": "20041010050500013M02606",
  "formatted": "FR14 2004 1010 0505 0001 3M02 606",
  "verdict": "valid",
  "checked_at": "2026-08-28T17:00:00.000Z"
}

The verdict field tells you why something failed rather than just that it did: valid, invalid_checksum, invalid_length, unknown_country or invalid_format. expected_length next to actual_length usually makes a bad paste obvious at a glance.

Pricing

Pay-per-event: $0.005 per IBAN checked, charged once a completed check is produced — valid or invalid alike, since finding out that an IBAN is wrong is exactly the answer you paid for.

Limitations — read this before you buy

• Structural validation only. A valid verdict means the IBAN is well-formed and its checksum is correct. It does not mean the account exists, is open, or belongs to the person you think. No bank is contacted; that is what makes this fully offline.
• There is no BIC/SWIFT derivation and no bank-name lookup.
• A country absent from the ISO 13616 registry returns unknown_country rather than a guess.

FAQ

Can a valid IBAN still fail a transfer? Yes. The checksum only proves the number is internally consistent. A closed account, a wrong beneficiary name or a bank-level rejection are all invisible to any offline validator.

Why not use a bank-lookup API instead? Because the overwhelming majority of bad IBANs are typos, and a mod-97 check catches those in microseconds without sending anyone's bank details to a third party.

Related Actors

Part of the same family of small, single-purpose checkers on this account — each does one thing, priced per item checked:

• Card Number Validator (Luhn) — Luhn checksum and card-network detection, output is masked.
• Barcode Check-Digit Validator — EAN-13, EAN-8 and UPC-A check digits.
• EU VAT Number Checker — official VIES lookup.
• Email Address Validator — syntax, domain and MX checks.
• Password Strength Checker — entropy scoring, never returns the password.
• Cron Expression Validator — plain-English description and next run times.
• French E-Invoice Partner Resolver — SIRET / SIREN / VAT resolution.