If you top up using Viking Points, the Viking Points mentioned on your invoice or payment invitation will only be the Viking Points you purchased and used for the top-up. Free Viking Points you used to top up, are a discount and can therefore not be invoiced. For example: for a € 15 top-up, you use 3 Viking Points your received (via a Viking Deal, through a referral, or somebody shared the Viking Points with you). Your invoice or payment invitation will then only mention the € 12 payment you did, not mentioning the free Viking Points you received.
Please note: as of 10 December 2017, you won't receive anymore invoices for prepaid SIM cards. More info here.