Article 1 defines the scope of the Top-up Tax, applying to Constituent Entities of MNE Groups with annual revenues of EUR 750 million or more in at least two of the four preceding fiscal years. It provides essential definitions for MNE Groups, Constituent Entities, and Ultimate Parent Entities (UPE). Crucially, it identifies Excluded Entities, such as governmental bodies, international organisations, and pension funds, which are generally exempt. The article also establishes specific rules for sovereign wealth funds and entities held by non-profit organisations, ensuring alignment with international Pillar Two standards.