The debate around the UK’s level of involvement in the EU single market after Brexit may lead to a significant u-turn in government policy. Having initially said it would not seek a customs union with the EU after Brexit (after leaving the full, existing customs union), it looks as though the UK government’s position is softening. Given the alternatives to the single market that are available to the UK, a potential u-turn is welcome.
Leaving the single market but agreeing to a customs union doesn’t rule out the UK making its own trade deals. However, it should be careful what it wishes for. Freedom comes at a price. A customs union only covers trade in goods, so the UK would need an umbrella agreement to cover its other arrangements with the EU.
The World Trade Organisation (WTO) sets out the basics in Article XXIV of the General Agreement of Tariffs and Trade (GATT). In essence, a customs union is where tariffs are removed between members of the union, and the tariffs charged on imports coming from outside the union are harmonised across members of the union. This definition seems straightforward but when you dig deeper into Article XXIV, you find that while these rules apply to trade in goods, they say nothing about services – which are of course very important for the UK.
Source: A customs union would free the UK to strike trade deals – but it doesn’t solve every Brexit problem : The Conversation