Quote from lorax2013:
I'm not an expert on this but... If you are a US citizen, then when you set up the offshore account or corporation you are perhaps still going to have to provide your American passport and tax ID. (you won't have British ID will you?) Therefore, I don't see any advantage in doing this from the UK or the USA. The IRS is cracking down harder every year on these offshore corps/accounts. Although it is my understanding that you can still hide a corporation in many offshore countries, this is changing rapidly. As for opening the account in the UK, my understanding is that all your info is reported straight to the IRS (only Americans have this problem because the US govt is able to put so much pressure on other countries to report). If you were from some nation besides "the land of the free" it wouldn't be a problem.
If you're a US citizen then you have US tax liability on global personal income, unless you renounce your citizenship. I assumed zentrader was not a US citizen, but I guess he might be and was just unaware of this draconian policy (which only N Korea and a few other hellholes other than the USA follow).
If he is USA, then the tax haven route is a lot less attractive. I am not familiar with US tax law but he may still be able to operate an offshore company to compound gains tax free before remitting them to the UK or wherever he ends up living.