Purpose The purpose of this paper is to review the economic studies on Brexit, highlighting that they have focused mainly on its negative impact on trade. The economic intuition behind these outcomes is provided, explaining why they are asymmetric with the UK being much more harmed than EU-27. Design/methodology/approach The importance of foreign multinationals in the UK and of UK’s multinationals abroad is shown using a non-standard quantification, which may be preferable than conventional methodologies. In addition, EU trade and investment legislative regimes are explained. Particular attention is paid to the change after the 2009 Lisbon Treaty which transfers foreign investment to the exclusive competence of the EU as opposed to EU states. Findings The data show that EU-27 is a much less important investment than trade partner for UK. Originality/value Although modelling the economy-wide impact of multinationals is challenging, the data and EU legislative framework analyzed suggest it is very much worthwhile. Other considerations about UK’s diminished leveraging power to negotiate after its EU’s withdrawal are also considered.