I don't know about a lot of countries but if you have earned your income in that country or through a business that had its ownership in that country you'll be taxed no matter where you go even if you are receiving it anywhere around the globe. But in the case of bitcoin finding the source of that income becomes really difficult in fact it's too debatable. Most of the countries work this way: If you leave the country for taking up employment elsewhere and you have lived in that country for less than half a year you are considered a non-resident. So whatever you would earn after leaving the country in that very year wouldn't be taxable. However, the incomes you earned during the tenure you were in the country would still be taxable.