How do I set up tax settings for UK and overseas customers?

[PhillipBunn]

I am a UK company new to shopify , we sell mainly in the UK  , But we also have lots of sales in EU and worldwide.

trying to figure out the settings in shopify so that my UK customers pay the 20% vat we need to charge , But my overseas customers should not pay and tax as it is collected by delivery company {fedex or post office etc}.

So for example an item that is £20inc vat here a customer in the USA would pay £18..

any help would be very welcome