Version 2.87 and up.
The following fields have been added to your media campaign and invoice and their line items:
Navigate to the Custom Settings and click on manage for VAT. Open the relevant record combination of seller, and buyer and type and add an external name/id: 
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Additionally you have to had a record for the VAT Exempt if you like to use an external name/id for the exempt value also: |
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The system then automatically populates the following fields on
MediaCampaign/Invoice:
VatExternalNameVatExempt__c
VAT External Name (Type 1)
VAT External Name (Type 2)
Campaign Item and Invoice Item:
VAT External Name