Under the EU VAT rules, service providers and their customers must determine, on the basis of the place-of-supply rules and the rules that define the scope of the reverse charge mechanism, whether they or their contracting parties are liable for remittance of the VAT due on cross-border services. The VAT liability may depend on circumstances that concern the contracting party. In this article, the author discusses the practical issues that may arise in this respect, especially where the two parties – on the basis of assumptions or their perception of the facts – assess the situation differently.