What happens when we have to apply the internal laws of Spain and another country as an individual is a resident of both?

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:

1. 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.
2. If the above criterion does not determine residence, the individual is considered resident in the country where he or she usually lives.
3. If the individual lives habitually in neither or both, they are a resident of the country that gave them their nationality.
4. If they have dual nationality of both countries, or of neither, the Authorities in question will resolve the case by mutual agreement.