We already have to record and report the details of everything we import and export as a business. Those telling you that it's massively different outside the EU are scaremongering.It's non-tariff barriers that are what we need to watch out for and are more difficult to overcome.
One of our suppliers (a US company) had a presence in France in order to be in the EU. About 5 years ago they ditched their french branch and served the EU from their Dubai base because the costs of being in the EU (tax, employment costs, red tape, etc) were significantly higher than the cost and effort of being outside.
They've halved their admin staff since moving, have taken more than half from associated costs and have never looked back.