I have dealt with UK companies trying to charge me VAT, although I am in the US. Some will drop it if I question it; others say "we have to!" In the US, it is not unusual for, say, a big box store that has just opened to be permitted to collect state and local sales tax but not have to actually turn it over to the government for a set amount of time, usually a couple of years. In NY, this amounts to a significant increase in profit, because our sales tax is pretty high. I wonder if these people have "affiliates," and if so, if that is the reason why they think they now will collect sales tax from customers in all the states where they have affiliates (that don't have a web presence that I can see).