In these cases, 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:
- 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.