Portugal: double taxation agreement, Article 24: Mutual agreement
(1) Where a resident of a Contracting State considers that the actions of one or both of the Contracting States result or will result for him in taxation not in accordance with this Convention, he may, notwithstanding the remedies provided by the national laws of those States, present his case to the competent authority of the Contracting State of which he is a resident.
(2) The competent authority shall endeavour, if the objection appears to it to be justified and if it is not itself able to arrive at an appropriate solution, to resolve the case by mutual agreement with the competent authority of the other Contracting State. with a view to the avoidance of taxation not in accordance with the Convention.
(3) The competent authorities of the Contracting States shall endeavour to resolve by mutual agreement any difficulties or doubts arising as to the interpretation or application of the Convention.
(4) The competent authorities of the Contracting States may communicate with each other directly for the purpose of reaching an agreement in the sense of the preceding paragraphs or for the purpose of giving effect to the provisions of the Convention.