Residence in two EU close countries

Question

Let us assume that a Spanish citizen settles with his family in Northern France and then decides somehow to settle also in a city in Belgium and for each country, he gets a residence permit for EEA citizens (which is optional).

Assuming that this person splits his life between Belgium and France and entertains administrative formalities in each country only with the residence permit of that country, would it be irregular law-wise?

Is there a data exchange between countries that can make such a person be in a problem, even though the person is assumed to use in each country only its own delivered card?

When it comes to taxes, if such person manages to work in both countries (combination of part-time and full time), would each of salaries be taxed only by the country it's generated from? (i.e French salary taxed by France and Belgian salary taxed by Belgium)? Or is it more complicated?

Answer 1

First, the residence card is a detail. It's not mandatory to get one (certainly in France, Belgium will expect some registration at the municipality) and doesn't fundamentally change your position.

Regarding taxes, there is a tax treaty with a series of tests (where your ties are your strongest, where you spend the most time, whether you are a French or Belgian citizen…) If those tests are not enough to decide, the two states should decide “in agreement” where you are deemed to have your primary residence.

Once that's decided, there are complex rules and exceptions for different types of income. But for a regular salary, the rule is indeed quite simple: it is taxed in the country where it's generated, French salary in France, Belgian salary in Belgium (cf. article 11). There are also some special rule for people who live the border area and historical rules that still apply to people who were already cross-border workers before 2011 but they don't seem to impact your scenario.