# IBAN\_VALID ### Description `IBAN_VALID` checks whether a string is a structurally valid IBAN (International Bank Account Number). It verifies the country code, length, and mod-97 checksum as defined by the [ISO 13616 standard](https://en.wikipedia.org/wiki/International_Bank_Account_Number). It does not verify whether the account actually exists. ### Syntax ``` IBAN_VALID(iban) ``` **Returns:** `true` if the IBAN is structurally valid, `false` otherwise. ### Example ``` IBAN_VALID('CH5604835012345678009') ``` This returns `true`. ``` IBAN_VALID('CH0000000000000000000') ``` This returns `false` — the checksum does not pass. ### Example in context ``` p is Person IBAN_VALID(p.bank_account_number) ``` Returns `true` if the account number entered by the user is a valid IBAN. Commonly used as a condition to trigger a validation error or block case progression until a correct IBAN is provided. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.atfinity.io/rule-language/operators/special-operators/iban_valid.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.