Today, as a traveller you don’t need to pay excise duty or tax on goods you bring in from the European Union (EU) if you: transport them yourself, will use them yourself or give them away as a gift and have paid duty and tax in the Country where they were purchased. When arriving home from a trip abroad, we are all accustomed to the “blue” channel at UK airports. You can bring any reasonable amount of alcohol or tobacco from the EU back to the UK, provide the local duties and taxes have been paid and that they are for personal consumption and not for resale.
That said, the rules governing customs are typically EU law and they are now directly applicable in the UK. Since the UK intends to leave the European single market and customs union this may get complicated and means that UK law must be changed.
If the outcome of Brexit is “No Deal”, and the UK crashes out of the EU on 29 March 2019 without any agreement in place, it becomes a “Third Country”. Thus, at a stroke, EU customs laws would no longer apply in the UK and duty between the two markets could be automatically returned.
So, the duty-free allowances are likely to change post-Brexit. In other words, the allowances may become the same for those returning from either the EU or outside the EU. This means losing the current more generous conditions, as quoted above. After Brexit, returning from an EU Country may the same as returning from a non-EU Country like the USA, UAE, Australia, India or Japan.
The days of the “booze cruise” where people go over to France or Belgium and stock-up with a car load drinks for personal consumption may come to an end. HMRC publishes information for arrivals from outside the EU. That information will no doubt be updated within the next 50 days.