The top-up tax otherwise due by an ultimate parent entity or an intermediate parent entity located in the State is reduced to zero for the first five years of the initial phase of an MNE group's international activity, notwithstanding the Chapter 5 requirements. The reduction also applies where the ultimate parent is located in a third‑country jurisdiction to the top-up tax due by a constituent entity located in the State. A five‑year reduction likewise applies to members of a large‑scale domestic group in the first five years, starting from the first day of the fiscal year in which the group first falls within the scope of this Part.

An MNE group is in its initial phase if it has constituent entities in no more than six jurisdictions and the sum of the net book values of tangible assets outside the reference jurisdiction does not exceed €50,000,000. The reference jurisdiction is the jurisdiction in which constituent entities hold the highest total value of tangible assets in the fiscal year the group originally falls within scope. The five‑year period begins at the start of that fiscal year, with transitional commencement dates of 31 December 2023 or 31 December 2024 for groups already within scope on commencement; where subsection (1) or (2) applies a filing constituent entity located in the State must inform the Revenue Commissioners of the start date of the initial phase.