Depends on your tax status.
20% withholding tax if you dont wish your details to be disclosed to your relevant authority. Pretty acedemic if you are a euro citizen really since browns raid on all off shore banks demanding full disclosure to hmrc. The bank (RBS) informed us after the disclosure although they had known about it months in avance So much for offshore. Just proving the fact that I didnt owe hmrc anything cost me £5000 in fees something I could have mitigated if forwarned with appropiate notice of their intended date.
Apart from that lovely people.
Its all in a tin in the back garden now.