Thanks for your question, it is very interesting and a question our client often have. I am an international business lawyer and often have to deal with this kind of situation.

To answer your question briefly, in general principles, your business is resident where is located your head office (which is in most case dictated by your governing law).

To answer your question fully, I think it would be helpful to know exactly why you need to establish "where is your business" since the interpretation principles may vary depending of the reason i.e. tax, corporate, contract, etc.