For income tax, the basic principles from which to start are that an individual who is resident in a country will generally be taxed in that country on their worldwide income, but regardless of residence, an individual who is physically present and working in a country will be liable to tax in that country on income received for performing that work.

From these principles, it immediately becomes clear that a person who is resident in one country while temporarily working in another country could be liable to tax in both countries in respect of the same income.