this could be the structure of the tables.

I am not sure what result your are looking for, but it sound like you could try to create a custom view where you join the two tables on vendor.vat = catalouge.vat

This would give you a view where you could probably build a 1-N relationship for both vendors and products

This is not an answer to your question but please fix the name of the Catalouge table (it should be Catalogue I guess). It's a royal pain in the behind to do it at a later stage when you've got several tabular models and 42 Power BI Reports using the incorrect name :)

that will be done :-D 

Hi,

how to approach this depends on what is needed. I would expect a product to have a VAT code of some sort as VAT depends on the product or type of service. There isn't really any logic behind allocating a VAT code to a vendor in my opinion. I expect the allocation of a VAT code to a vendor to be an emergent data point and not truly “real”.

You could create a view/table of all vendors linked to a code, or all codes linked to a vendor, or both, but the question is what you need and whether it makes sense to use this data to create that.