All countries have customs checks, to check that incoming goods conform with regulations, applicable tariffs are paid, etc.
Except countries in the EU, which has a common market that made such checks unnecessary inside of it. Of course there are still customs on the outside EU border.
So if you leave that, and your borders are now not internal market borders anymore but your and the EU's external borders, you're going to do more customs checks than you used to have. In both directions.
Except countries in the EU, which has a common market that made such checks unnecessary inside of it. Of course there are still customs on the outside EU border.
So if you leave that, and your borders are now not internal market borders anymore but your and the EU's external borders, you're going to do more customs checks than you used to have. In both directions.