Once you reach a specific selling threshold in a European country you are bound to register a VAT number and pay VAT in that specific country.
VAT Guard monitors your sales threshold in all European countries. You can, therefore, predict when you will reach the threshold in a specific country. The data is pulled from your Amazon account automatically is refreshed everyone month.
Once you reach the threshold in a country you need to provide a sales invoice proving you reached the limit or are close to reaching it the system informs you automatically asking you for applying for a new VAT number.