In the cases of residence in two countries, the agreement or treaty between the two countries should be consulted, if one is in place. These treaties establish rules to prevent that a person is considered a resident of both countries from a taxation viewpoint. In general, these rules state that an individual is a resident:
The period of validity of these certificates is one year.
However, the certificate’s validity shall be indefinite if the entity subject to tax is a foreign country, one of its political or administrative or local entities.
Of the country where he or she has a permanent residence. If he or she has a permanent residence in both countries, they are considered a resident of the country with which they hold the closest personal and economic ties.
If the above criterion does not determine residence, the individual is considered resident in the country where he or she usually lives.
If the individual lives habitually in neither or both, they are a resident of the country that gave them their nationality.
If they have dual nationality of both countries, or of neither, the Authorities in question will resolve the case by mutual agreement.