IBAN Checker: Validate and Generate Test IBANs

How to use the iban validator

1. Select Validate mode and paste or type an IBAN into the field.
2. The iban checker strips spaces, verifies the country-specific length and runs the mod-97 checksum.
3. Review the verdict, formatted display, country code and BBAN in the results.
4. Switch to Generate mode, pick a country and click Generate to create a random test IBAN.

How the IBAN checksum works

The IBAN standard (ISO 13616) uses a mod-97 algorithm to detect transcription errors. To validate, strip all spaces and convert to uppercase. Move the first four characters (country code and check digits) to the end. Replace each letter with two digits where A equals 10, B equals 11, up to Z equals 35. Finally, compute the remainder when dividing the resulting large number by 97. If the remainder is exactly 1, the IBAN passes the iban check.

For example, take GB82WEST12345698765432. Rearranging gives WEST12345698765432GB82. Converting letters yields 3214282912345698765432161182. Computing this modulo 97 produces 1, confirming the number is structurally valid.

Supported countries and lengths

This iban validator supports 25 European countries. An IBAN from any other country returns an unsupported country message rather than a verdict. Each country has a fixed total IBAN length including the two-letter country code and two check digits.

The validator checks length and the mod-97 checksum. It does not check the country-specific bank code or account structure.

Generating test IBANs

The built-in iban generator creates a random BBAN (Basic Bank Account Number) of the correct length for the selected country, then computes the two check digits using the formula 98 - (rearranged number mod 97), padded to two digits if necessary. For GB and IE it uses 4 letters followed by 14 digits, for NL 4 letters followed by a 10 digit account number that passes the 11-test, for IT a check letter computed from the rest, and for FR and BE the national check digits. Other countries get random digits, so those numbers pass the mod-97 check but not necessarily national account rules.

Important: every generated IBAN is strictly test data only, not real. These numbers are randomly assembled and are not guaranteed to be unassigned. Never use them for real transactions or share them as genuine account details.

Common mistakes when checking IBANs

A frequent error is entering lowercase letters or leaving spaces inside the string. The iban checker automatically normalizes input by uppercasing and stripping spaces before validation. Another common issue is confusing the country-specific BBAN format with the full IBAN. For instance, a UK sort code and account number alone are not an IBAN until prefixed with GB and the correct check digits.

Length mismatches also cause failures. If you enter a German IBAN with 21 characters instead of the required 22, the tool will flag it immediately. Always double-check that no digits were dropped during copy and paste.

Related financial validators

While this tool handles international bank account numbers, other formats require different algorithms. For payment card numbers, use the credit card checker which applies the Luhn algorithm. For US domestic wire transfers, the ABA routing number checker validates the nine-digit routing codes used by American banks. Each standard uses its own checksum logic, so a number that passes one validator will not necessarily pass another.

Worked examples