If you buy the Viking Points, they’ll be marked as a gift on your invoice.
If you receive the Viking Points, they will be marked on your invoice as soon as you exchange the Viking Points for calling credit and effectively use your calling credit. From that moment, it’ll also be possible to calculate the necessary VAT.
Please note: as of 10 December 2017, you won't receive anymore invoices for prepaid SIM cards. More info here.