US Withholding Tax


Following on from the other post about Capital Gains etc...

Does anyone know how the tax regime works for US shares. Whenever I have been given shares at work (US company) I have had to pay US 'Withholding Tax'.

Does the same apply if we trade the e-mini through Interactive Brokers? I have filled in my W8-BEN, but do the US government still tax me? Do they pass my details onto the Inland Revenue? I had to fill in a huge amount of info for IB, including my NI number, so they can clearly identify me.

Obviously I dont want people to identify themselves or their methods (in case the IR is watching :mad: ) but any general guidelines would be gratefully accepted. PM or Email if necessary.

W8-BEN simply excuses you from US tax.
Years ago on ESI (which became Etrade), Greystone asked what people did for a living and I jocularly said I was a Special Compliance Officer for Her Majesty's Inland Revenue.
I lost all my buddies instantly ;-)