Pillar Two: Operationalising the Global Minimum Tax and Its Implications for International Holding Structures

With the widespread implementation of the GloBE Rules (Global Anti-Base Erosion Rules), the international tax landscape has undergone a tectonic shift comparable in structural significance to the introduction of the OECD Model Tax Convention in the 1970s. Since early 2024, more than 50 states — including all EU Member States as well as the United Kingdom, Japan, Canada and Australia — have enacted Pillar Two legislation; key hubs such as Singapore and the United Arab Emirates are set to follow on January 1, 2025. The central effect is unequivocal: multinational enterprise groups with consolidated revenues exceeding €750 million must pay an effective minimum tax rate (ETR) of 15% on their profits in every jurisdiction where they operate. What appears abstract in theory carries immediate and substantial practical consequences for established holding architectures, financing structures and location decisions of multinational corporations.

The Three Pillars of the GloBE Framework: IIR, UTPR and QDMTT

The technical foundation of Pillar Two consists of three interlocking mechanisms. The Income Inclusion Rule (IIR) obliges the parent entity of a multinational group to pay a top-up tax on low-taxed income of subsidiaries where their effective tax rate falls below the minimum rate of 15%. The calculation follows not the nominal tax rate of a jurisdiction, but the actual qualified tax rate paid on GloBE income — a concept that is considerably more complex than it appears, given specific exclusions and adjustments (Substance-Based Income Exclusion, Excluded Entities).

The IIR is supplemented by the Undertaxed Profits Rule (UTPR), which operates as a backstop where the IIR cannot be applied — for example, because the parent entity is resident in a jurisdiction that has not enacted Pillar Two legislation. The UTPR allows other group entities to levy a corresponding top-up tax. Finally, the Qualified Domestic Minimum Top-up Tax (QDMTT) permits individual jurisdictions to impose their own national minimum tax credited against the GloBE tax liability. Jurisdictions such as the UAE, the United Kingdom and Luxembourg have availed themselves of this option — a strategic move that retains tax revenues domestically while protecting the group from an IIR charge at the parent entity's level.

Substance-Based Income Exclusion: The Critical Buffer for Operative Structures

For the practice of holding planning, the Substance-Based Income Exclusion (SBIE) is critical. It exempts certain profit portions attributable to genuine economic activity from the top-up tax. Specifically, 5% of payroll costs for qualified employees and 5% of the carrying value of qualified tangible assets in a given jurisdiction are deducted from the GloBE tax base. For the transitional period until 2033, elevated percentages apply (initially 10% on payroll costs and 8% on assets). This means: holding companies with genuine economic substance — own personnel, own office premises and operative decision-making — can keep their effective Pillar Two tax burden well below 15% without breaching the framework.

This mechanism has fundamentally altered location decisions. Pure letter-box structures without an operational core cannot claim the SBIE and face a considerable GloBE tax burden. Conversely, jurisdictions such as Ireland, the Netherlands, Luxembourg and the UAE (with their QDMTT solution) are experiencing repositioning as substance locations, where the combination of attractive nominal tax rates and demonstrable economic presence yields a regulatory-resilient holding jurisdiction.

Implications for Intra-Group Financing Structures

Pillar Two generates particular complexity in the area of intra-group financing. Traditional structures routing loans through low-taxed intermediary companies (e.g., in Luxembourg, the Netherlands or Malta) to concentrate interest income in a favourable tax regime are fundamentally challenged by the GloBE system. The Subject-to-Tax Rule (STTR) — a bilateral instrument that can be incorporated into double tax treaties — permits source states to levy withholding taxes on certain intra-group payments where the recipient state taxes them at less than 9%. For group-wide treasury structures, this requires a comprehensive review of interest payment flows.

Moreover, Pillar Two affects the tax qualification of hybrid financing instruments. Instruments classified as equity in one state and debt in another (hybrid instruments) already carry risks of disallowed deductions under ATAD II. Under Pillar Two, GloBE-specific qualification issues arise additionally, which may affect the effective tax rate at the recipient entity level and thereby alter the calculation of the top-up amount.

Safe Harbours: Practical Relief During the Transitional Phase

The OECD has developed several safe harbour provisions to mitigate implementation complexity. The transitional CbCR safe harbour allows enterprise groups to use their existing Country-by-Country Reporting data to perform a simplified test of whether a jurisdiction is even GloBE-relevant. Jurisdictions with an effective tax rate above 15% under this simplified calculation need not be included in the full GloBE computation for the transitional period. For mid-sized and smaller enterprise groups within the scope of the rules, this represents a significant reduction in compliance burden — albeit subject to strict data-consistency requirements.

In parallel, the European Commission has adopted several administratively simplifying measures supplementing the Pillar Two Directive (2022/2523/EU), aimed particularly at reducing double taxation risks and achieving coherence between national regimes and OECD guidance. Nevertheless, considerable implementation divergence persists between Member States — particularly in the treatment of tax credits, losses and the definition of qualified taxes.

Strategic Repositioning: Which Jurisdictions Benefit?

Pillar Two implementation has produced a clear winner-loser picture. Winners are jurisdictions that first have nominal tax rates of 15% or above (and thus do not generate top-up tax obligations from the outset), second have introduced a QDMTT (retaining tax revenue domestically) and third can satisfy genuine substance requirements. In this profile, the UAE (9% CIT + QDMTT), Ireland (12.5% / 15% post-Pillar Two + QDMTT), Luxembourg and Singapore position themselves as strategically attractive. Under pressure, by contrast, are classic low-tax regimes such as certain Caribbean or Pacific jurisdictions, which could not enforce genuine substance requirements and now face a foreign top-up tax charge.

For operative holding planning, a clear imperative follows: location decisions must henceforth be assessed primarily by reference to GloBE compliance and substance capability. The question is no longer only "What tax rate applies?" — but: "Can our holding jurisdiction generate a robust substance exclusion, and is its QDMTT solution internationally recognised?"

Compliance Challenges: The GloBE Information Return

Multinational enterprise groups are subject to a comprehensive reporting obligation under Pillar Two: the GloBE Information Return, which must disclose the effective tax rate, GloBE income, qualified taxes and the substance-based exclusion for each jurisdiction. This return must be filed for fiscal years from 2024 in all implementing jurisdictions. It places high demands on the quality of tax data governance and requires substantial investment in ERP systems and tax data management. At group level, a new layer of compliance costs is thereby created — particularly significant for mid-sized enterprise groups at the margins of the €750 million threshold.