How to Validate an IBAN?
IBAN validation consists of three steps: the length, character and MOD-97 checksum check. This guide explains each step and notes the limits of validation.
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Quick answer
IBAN validation has three steps: the length, character and MOD-97 checksum check.
These checks catch typing errors to a large extent. But a valid IBAN does not prove that the account actually exists or is active.
Validating an IBAN before sending is the simplest way to protect yourself from misdirected transfers and return costs. In this guide we explain how IBAN validation is done, in three steps.
Step 1 — Length check
Each country's IBAN length is fixed: Germany 22, France 27, the Netherlands 18, Turkey 26 characters. The first check is whether the IBAN is the correct length for its country code. A wrong length is most likely a typing error.
Step 2 — Character and structure check
An IBAN consists only of letters and digits; spaces are ignored. The first two characters must be a valid country code (two letters), and the next two characters must be a two-digit check number. These structural checks catch basic format errors.
Step 3 — MOD-97 checksum
The heart of IBAN validation is the MOD-97 (ISO 7064) check. It works as follows: the first four characters are moved to the end, the letters are converted into numbers (A=10 … Z=35), and the remainder of dividing the resulting large number by 97 is calculated. In a valid IBAN this remainder must be 1. When a single digit or letter is entered incorrectly, this check most likely flags the IBAN as invalid. To do these three steps automatically in your browser, you can use the IBAN validation tool; the tool also shows the country, the SEPA scope and (for Germany) the BLZ/account split.
An important limit
These three steps check the structural and mathematical validity of the IBAN; they do not show that the account actually exists or is active. A wrong but valid IBAN is also possible. That is why you should confirm the recipient's details separately and, if you receive a payee name–IBAN mismatch warning, take it seriously. For privacy, our tools do not send your IBAN to any server; the calculation is done in your browser.
Summary
IBAN validation consists of the length, character and MOD-97 checksum check. These checks catch typing errors but do not prove that the account is active. Validating the IBAN before sending and confirming the recipient's details is the most effective way to protect yourself from a misdirected transfer.
Frequently asked questions
How do you validate an IBAN?
In three steps: (1) length check (each country's IBAN length is fixed), (2) character check (letters and digits only), (3) MOD-97 checksum (ISO 7064). These checks catch typing errors. Our IBAN validation tool does this in the browser.
What is MOD-97?
It is the mathematical check method inside the IBAN. The first four characters are moved to the end, the letters are converted into numbers, and the remainder of dividing the resulting large number by 97 must be 1. If the remainder is not 1, the IBAN is invalid.
Does validation show that the account is real?
No. Validation is only a structural and checksum check; it does not prove that the account actually exists or is active. Confirm the recipient's details separately.
Sources
Confidence is graded from A (official document) to E (unverified).