I would check first whether the US tax authorities will consider that a UK based web business has any tax liability in the US. I doubt it but Google u201cUSA accountants in the UKu201d.If you need to do tax returns then you will need an ITIN number: Go to General ITIN Information for clarification.As someone else has mentioned the system has been changed recently and we had to prove our identity when last in the USA in order to get a new number.