If you are situated within EU and buy or sell to companies in other EU countries, you will be happy to hear there's already a suitable tool available for you which will enable you to verify any VAT number within EU.
A Finnish VAT registration number/organization number (FO number) has 8 digits. Please also note, the international VAT registration number begins with "FI". If you have FO-number 00000000, your VAT number will be:
Check domestic FO numbers here.
Another option for validating a VAT number:
Phone: (00358) 029 497 062
When invoicing without VAT to another company within the EU, you will need a valid EU-VAT number from the customer and then print it on the invoice. If, as an example, your French customer does not have a valid VAT number, you will need to assume it's a private person and apply VAT on the invoice. Therefore it's important to check the EU VAT number.
It took a while, but in the end, an entrepreneur had enough and created their own service for checking multiple VAT numbers at once.
Check multiple VAT numbers at the same time here!
The VAT numbers start with two letters indicating the country of origin, i.e. FR for France. The number of digits varies from country to country and can even end with a letter like "Z". But they always start with the 2-letter country code that is the same two letters that are used for country-specific domain names like alvtieto.FI for a Finnish website, momsviden.DK for a danish, dermwst.DE for a German, or momsens.SE for a Swedish site.