Tax implications of outsourcing/offshoring?

I wonder what the tax implications of outsourcing are, when the outsourcing is done offshore. If a company X pays company Y in another country to perform a task, I guess company Y does not have to pay taxes to the government to which company X has tax liability to. Is this different if company Y has a base in the country company X is located in? What is a person living in the same country as the original company receives a contract and sends it to his company Y in the second country - where does this person pay income tax for this contract?

I need to check up with my friends with MBAs or ppl in the offshoring business for this.