How much whiskey can you bring back to the US from Scotland?

One litre per person aged 21 or over. That is the federal personal exemption, and since a UK bottle is 700 ml it means one bottle comfortably, or a bottle and a large miniature.

Going over it is not an offence and does not get anything confiscated. What happens is that the excess becomes dutiable, and the duty on spirits for personal use is small — in practice a few dollars a bottle. Travellers routinely bring three or four bottles home and pay either a token amount or, quite often, nothing at all because the officer waves them through.

The important part is the declaration. Declare it. Writing the bottles on your customs form costs you a few dollars at worst; not declaring them is a different category of problem entirely and is never worth it.

One more wrinkle Americans forget: individual states set their own limits on personal importation, and a handful are stricter than the federal rule. If you are landing somewhere with tight alcohol laws, it is worth thirty seconds of checking.

This is the rule people do not know exists, and it is stricter than customs.

Alcoholic drinks between 24 and 70 per cent alcohol by volume are limited to five litres per passenger in checked baggage, and they must be in unopened retail packaging. Scotch is bottled at forty per cent and up, so it sits squarely in this band. Five litres is about seven UK bottles.

Drinks under 24 per cent — liqueurs, cream whiskies, most wine — have no such limit.

Drinks over 70 per cent are forbidden outright, in checked and cabin baggage alike. This is worth knowing because a few cask-strength whiskies genuinely exceed it, and a bottle at 71 per cent cannot legally fly at all.

And bottles cannot go in your carry-on, because of the 100 ml liquids rule. The single exception is duty free bought airside after security, sealed in a tamper-evident bag with the receipt visible — and even that can be taken off you if you have a connection that sends you back through a security check.

Sometimes, and it is more complicated than carrying it.

Alcohol shipping into the United States is regulated at state level as well as federal, and the rules differ a great deal from one state to the next. Some states permit direct receipt of spirits by an individual; several do not permit it at all. The ordinary international couriers generally will not carry alcohol for private customers, which is why the offer usually comes from the shop rather than from you.

Where a specialist retailer offers shipping to the US, they are working through a licensed import route and the cost reflects it: shipping plus federal excise plus state tax can add more than the bottle. For one or two bottles it is almost never worth it.

Where it does make sense is for something genuinely unavailable at home — a distillery-exclusive bottling, a cask-strength single-cask release — and for people buying enough that the fixed costs spread out.

For everybody else: check a bag, pack it properly, declare it, and pay a few dollars of duty if you go over the litre. That is the cheapest and simplest route by a distance.