The EU is an example of a customs union - Leaving Cert Economics - Question 3 - 2018

A customs union is an agreement between member countries to eliminate trade barriers and adopt a common external tariff on goods imported from non-member countries. This means that within the customs union, member states agree not to impose tariffs on each other's goods, facilitating free trade among them.

Furthermore, they collectively enforce a common tariff on imports from countries outside the union, ensuring that all member countries apply the same duties and regulatioms on goods entering the union. This arrangement allows for greater economic integration and cooperation among member states, which can enhance trade efficiency and strengthen economic ties.