# VAT Number Validation BestInvoicing allows you to easily look up a VAT number for a customer or supplier. BestInvoicing is connected to the [VIES](https://ec.europa.eu/taxation_customs/vies/) system of the European Union: all European VAT numbers can be searched and matching company data will automatically be retrieved. Company data can be found based on VAT number during the creation of a customer file or creation of a document. Simply fill the VAT number of your customer in the corresponding BestInvoicing field and click the 'Validate' button. ## F.A.Q. ### Q: An error message is displayed: "Service Unavailable" A: If there are issues with the [VIES service](https://ec.europa.eu/taxation_customs/vies/) (e.g. offline, connection problems, ...) that prevent BestInvoicing from communicatign with the system, VAT validation can not be executed/data can not be retrieved. You can test via the [VIES website](https://ec.europa.eu/taxation_customs/vies/) whether or not there are current service issues. ### Q: An error message is displayed: "Structure Invalid" A: A VAT number always starts with a country code, followed by the company registration number. For Belgium, every VAT number starts with 'BE0', followed by the 9-digit company registration number. Some entrepreneurs mix the two numbers up and forget the country code, which is necessary for validation. ### Q: Although the VAT number is 'valid', no company data is retrieved? A: Not every member state of the European Union offers a public database containing the address data of companies. For Spanish VAT numbers for example, VIES only communicates whether the VAT number is valid or not, but does not share any company address data. --- # 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://support.onfact.eu/more-features/vat-number-validation.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.