Tax assessments are a source of deep insight for both companies and workers involved in international mobilisation dynamics. Where will I pay taxes? Should I transfer my residence abroad? And what are the consequences of these choices? Or, what favourable tax policies can be applied to individuals posted abroad in order to make it easier for them to move, facilitate the conduct of business abroad and not create additional burdens for those involved?

These questions can often be answered through the double taxation treaties signed between the states involved (place of origin and place of work). These conventions contain several provisions signed by two contracting states in a variety of tax-relevant matters between two states. As a mere indication and to give concreteness, the treaties indicate:

• the subjective conditions that qualify a subject as a resident of a given State, rather than liable to double tax residence (there are many resolutions of the Italian Revenue Agency and issues concerning the interpretation and application of the so-called tie breaker rules);
• the conditions and modalities for the recovery of a tax credit (generated by the tax liability of the same income according to the tax provisions of both signatory States of the convention relevant to the case at hand.

Unlike in the social sec...