Hello.

To indicate VAT that shell be used in those cases you use VAT zones. VAT zone set on Invoice shell be according to the country items or services are delivered to. In case items are delivered to one and only place for your customer main VAT zone set on their record is used for your sales invoices. In case you deliver to different locations/countries for this customer for each of them you define Delivery address in SO>>Settings>>Delivery address and set on each address record VAT zone that is appropriate for country you send to. VAT zone from delivery address is used as main in case Delivery address is entered to the document and overwrites VAT zone from customer record. Based on VAT zone used, system will assign proper VAT code.

I hope this answer is covering your question.

Agnieszka