IBAN Validator

An International Bank Account Number, or IBAN, is a standardized way to identify a bank account across borders. It was created so that payments between countries could be routed and checked reliably, cutting down on errors that delay or misdirect transfers. The format follows the ISO 13616 standard.

Every IBAN starts with a two-letter country code, followed by two check digits, then a country-specific block called the Basic Bank Account Number, or BBAN. The BBAN holds the bank identifier, branch code where used, and the account number itself.

Length is fixed per country but varies between them. A German IBAN is 22 characters, while a Norwegian one is 15 and a Maltese one reaches 31. This validator knows the expected length for each participating country, so it can flag an IBAN that is too short or too long before it ever reaches a bank. That single check catches a large share of copy-and-paste mistakes, since dropping or adding a character is one of the easiest errors to make when handling a long string of letters and digits.

Validation runs several checks in sequence. First the tool confirms the country code is real and that the total length matches what that country expects. A mismatch here is the most common sign of a typo or a missing character.

The core test is the MOD 97 check digit algorithm defined in ISO 7064. The first four characters are moved to the end of the string, letters are converted to numbers using a fixed scheme where A is 10 and Z is 35, and the whole value is divided by 97. A valid IBAN always leaves a remainder of exactly 1.

This single arithmetic test catches the vast majority of accidental errors, including transposed digits and single wrong characters. When a check fails, the validator points to the stage that broke, so you can see whether the problem is the country, the length, or the check digits rather than guessing.

The clearest case is before sending an international wire transfer. A wrong IBAN can bounce a payment, delay it for days, or in rare cases send money to the wrong account. Checking the number first removes a common and costly source of error.

Payment processing systems lean on validation too. Any software that accepts bank details, from invoicing tools to payroll, benefits from rejecting malformed IBANs at the point of entry rather than failing later in a settlement run.

Simple data entry is the third case. When someone types an IBAN by hand, a single slip can break it, and the MOD 97 check catches most of these instantly before the number is saved. If you handle many numbers at once, such as a list of supplier or customer accounts, the Bulk IBAN Validator processes a full list in one pass instead of one at a time. Validating early, whether one number or thousands, keeps clean data flowing through every downstream step and avoids the far larger cost of chasing a failed payment after the fact.

An IBAN and a SWIFT or BIC code do different jobs, and payments often need both. The IBAN identifies the specific account, while the SWIFT/BIC code identifies the bank within the global messaging network. Think of the BIC as the address of the institution and the IBAN as the address of the account inside it.

In the United States, banks use a different system entirely. A routing number identifies the bank, and a separate account number identifies the account, with no single combined string like an IBAN. This is why US transfers ask for routing and account numbers rather than an IBAN.

The table below summarizes the difference.

Most failures come from simple human error. A transposed pair of digits, a missing character, or an extra space can all break the MOD 97 check even when every digit looks right at a glance. The validator catches these because the algorithm is sensitive to the exact order and value of each character.

Length mistakes are common too. Pasting an IBAN from an email or document sometimes drops a character or adds a stray one, leaving a string that no longer matches the country's fixed length.

An unsupported country code is another reason. Not every country uses the IBAN system, so a number formatted to look like an IBAN from a non-participating country will not validate no matter how carefully it is typed. When the tool reports a failure, it identifies which stage broke, so you can correct the specific problem rather than re-entering the whole number and hoping it works the second time. That targeted feedback turns a frustrating guessing game into a quick, focused fix, which matters most when a payment deadline is close.