Under Art. 203 of the EU VAT Directive, any person who enters VAT on an invoice must remit it to the tax authorities. In this article, the author analyses the history of that legal provision and discusses the case law of the European Court of Justice (ECJ) relevant in this framework. He also examines the conditions under which the tax authorities must refund unlawfully charged VAT or may deny refund applications on the basis of the doctrine of unjust enrichment.