The concept of the EU single market logically implies the adoption of a common external position on matters which it is primarily concerned with. In respect of goods and capital, such a position has gradually been formulated. With regard to people and services, national priorities continue to prevent the adoption of a united stance externally. Concentrating on the EU’s commitments under the WTO’s GATS Agreement, this article explains how the lack of a common position is due to the incomplete harmonisation of the internal market. This is especially evident in the case of the so-called ‘Mode 4’ that regulates the cross-border movement of natural persons supplying services. As long as the internal market is incomplete, the EU’s offer in respect of service trade negotiations remains fragmented along national lines. A single EU offer also poses the risk that the lowest common denominator becomes the basis of the EU’s common position.