That may be true in some countries, but not all. When I was based in Canada, working on projects in the States, and paid in Canadian dollars, if I spent more than a certain amount of time in the US (I think it was 180 days), I was liable for taxes in the US. Due to the Canada/US tax treaty, I was not taxed twice, but I had to show that I had payed taxes in Canada equal or greater than what I owed in the States (not hard).