Cross-Border Substance Requirements in 2026: What Changed and Where

Why 2026 marks a genuine inflection point

Substance requirements are not new. The OECD's Base Erosion and Profit Shifting project flagged artificial profit-shifting structures more than a decade ago, and the EU Anti-Tax Avoidance Directives began constraining intra-group arrangements well before the current cycle. What has changed in 2025 and 2026 is enforcement density: tax authorities in all four jurisdictions examined here have moved from issuing guidance to conducting audits, exchanging data under CRS and FATCA frameworks, and, in some cases, denying treaty-reduced withholding at source rather than reclaiming tax after the fact. For families operating multi-jurisdictional holding structures, the practical consequence is that a structure designed in 2019 or even 2022 may no longer satisfy the expectations of either the residence jurisdiction or the source jurisdiction from which dividends, interest, or royalties flow.

The OECD BEPS Pillar Two framework compounds the pressure. The 15% global minimum effective tax rate, now enacted into domestic law across EU member states and in a growing number of non-EU jurisdictions, means that low-taxed intermediate entities no longer merely attract scrutiny under anti-avoidance rules; they may generate a direct top-up tax liability in the ultimate parent's jurisdiction. For families whose structures sit inside Luxembourg SCSps or Swiss intermediate holding companies paying effective rates below 15%, the interaction between Pillar Two and substance rules has become the central planning challenge of this cycle.

Luxembourg: ATAD III transposition and the Pillar Two overlay

Luxembourg remains the dominant jurisdiction for European family-office fund structures, hosting a disproportionate share of SCSp limited partnerships and SOPARFI holding companies. Its attraction has always rested partly on an extensive treaty network and partly on a sophisticated fund-services industry. Both advantages are now conditioned on meeting a higher substance threshold.

The ATAD III direction of travel

The European Commission's proposed ATAD III, colloquially known as the UNSHELL Directive, has progressed through the legislative process with amendments that narrow its scope compared with the original 2022 draft, but the underlying logic has already influenced how the Luxembourg tax authority (Administration des contributions directes, or ACD) approaches rulings and audits. Entities that receive more than 65% of their income from passive sources and that cross-border more than 55% of their income will face a rebuttable presumption of lacking genuine substance. For a typical SOPARFI receiving dividends from operating subsidiaries and holding real assets, this threshold is easily crossed. The practical implication is that Luxembourg holding entities now require at minimum two full-time equivalent qualified directors resident in Luxembourg, a physical office that is not merely a registered address, and documented board-level decision-making on all material transactions.

The ACD has also revised its administrative practice on advance tax rulings. Rulings granted before 2023 that relied on thin-staffed holding companies are being reviewed on renewal, and several families have been informed informally that historical rulings will not be extended without evidence of upgraded substance. Families should treat any ruling older than three years as potentially vulnerable.

Pillar Two top-up tax exposure in Luxembourg structures

Luxembourg enacted Pillar Two into domestic law with effect from 1 January 2024, in line with the EU Minimum Tax Directive. A Luxembourg SOPARFI paying an effective corporate tax rate of approximately 18% to 19% on passive income sits above the 15% threshold and does not itself generate a top-up liability. However, intermediate entities held through the SOPARFI in lower-tax jurisdictions, such as certain UAE free-zone entities or offshore feeder vehicles, may generate a top-up tax collected in Luxembourg as the highest-tier EU entity. Families that stacked jurisdictions for effective-rate arbitrage in the pre-Pillar Two era must now model the consolidated effective tax rate across the entire ownership chain, not merely at the Luxembourg level.

Singapore: the Enhanced Tier Fund and MAS enforcement posture

Singapore's family-office ecosystem expanded rapidly between 2019 and 2023, driven by the Section 13O and Section 13U tax incentive frameworks administered by the Monetary Authority of Singapore. By late 2022, the MAS had approved over 1,100 single-family office structures under these schemes. The growth prompted a policy recalibration, and the revised conditions introduced in 2023 and further clarified in 2025 represent a substantive tightening.

Minimum AUM, local investment, and headcount requirements

Under the current Enhanced Tier Fund framework (Section 13U), structures must maintain a minimum fund size of SGD 50 million, deploy at least SGD 200,000 annually in local business expenditure, and ensure that at least one investment professional is a Singapore-based resident. For ultra-high-net-worth families seeking a lower entry point via Section 13O, the fund size threshold sits at SGD 10 million with a commitment to grow to SGD 20 million within two years, and the local hiring requirement applies equally. These thresholds are not merely administrative; MAS conducts periodic reviews, and structures that fall below the AUM floor or fail the expenditure test during a review period risk revocation of exempt status and retrospective taxation of previously exempt gains.

The MAS has also communicated a clear position on nominee directors and offshore decision-making. In correspondence with applicants and in its published FAQ updates from 2024, the authority has indicated that structures where investment decisions are demonstrably made outside Singapore, with a Singapore-based professional merely executing instructions, will not satisfy the substance requirement. This is a direct challenge to a common arrangement in which a family's principal advisor sits in Hong Kong or Switzerland while a locally engaged professional handles administrative compliance. Families must be able to show that the Singapore-based professional exercises genuine discretion over at least a portion of the portfolio.

The UAE: Corporate Tax Law and the qualifying income regime

The UAE's introduction of a 9% federal corporate tax from June 2023 marked the end of its status as a zero-tax domicile for operating and holding entities. The more consequential change for family-office structures, however, is the qualifying income exemption framework established under Ministerial Decision No. 83 of 2023 and subsequently refined through Federal Tax Authority guidance issued in late 2024 and early 2025.

Free-zone entities and the genuine activity test

Free-zone entities that satisfy the Qualifying Free Zone Person criteria remain eligible for a 0% rate on qualifying income, which includes dividends from subsidiaries and certain intra-group service income. The central substance condition requires that the entity undertakes its core income-generating activities in the free zone, maintains adequate assets, employs an adequate number of qualified employees, and incurs an adequate level of operating expenditure within the UAE. The Federal Tax Authority has not published bright-line quantitative thresholds for adequacy, which creates interpretive risk. Based on the guidance that has been issued, practitioner consensus places the minimum at two to three senior qualified professionals resident in the UAE with demonstrable decision-making authority, annual operating expenditure of at least AED 500,000 for a structure managing assets above AED 50 million, and physical office space under a genuine lease.

The outsourcing carve-out is narrow. A free-zone entity may outsource certain functions to related or third-party service providers within the UAE, but the core management and control functions, specifically investment decision-making and risk management, must remain with the entity's own qualified employees. Families that established UAE family-office vehicles purely as tax-efficient holding structures, with management residing in Europe or Asia, face the starkest substance gap under the current rules.

Switzerland: principal structures and treaty-access conditionality

Switzerland's position as a family-office domicile rests on a combination of political stability, legal certainty, and an extensive treaty network covering more than 100 jurisdictions. The Federal Tax Administration's evolving practice on principal structures and its application of the principal purpose test under updated bilateral treaties have introduced meaningful uncertainty for families that treated Switzerland as a holding location without building genuine operational substance.

The principal purpose test in Swiss treaty practice

Switzerland has incorporated the principal purpose test from the OECD's Multilateral Instrument into the majority of its updated bilateral tax treaties. Under this test, treaty benefits may be denied if it is reasonable to conclude that obtaining the benefit was one of the principal purposes of an arrangement. The Federal Tax Administration has applied this test actively in rulings since 2024, and advisors report that the administration now conditions favourable withholding rate confirmations on evidence that the Swiss entity has at least two Swiss-resident board members with the professional capacity to evaluate the transactions generating the relevant income, that board meetings occur physically in Switzerland with documented deliberation, and that the entity incurs meaningful Swiss operating expenditure proportionate to the income it receives.

The proportionality principle is the most practically challenging aspect of Swiss practice. A Swiss intermediate holding company receiving CHF 10 million in annual dividends from a portfolio of operating subsidiaries will be expected to demonstrate Swiss-side costs that are meaningful relative to that income flow. A total annual Swiss expenditure of CHF 150,000 to CHF 250,000, covering board fees, office costs, and professional services, is broadly consistent with the levels the Federal Tax Administration has accepted in recent rulings for structures of this scale. Below that range, treaty-access risk increases materially.

A four-layer framework for demonstrable substance

Across all four jurisdictions, a consistent analytical framework has emerged from regulatory guidance, audit practice, and adviser experience. It organises substance into four layers: people, place, process, and proof.

The people layer requires qualified, senior professionals resident in the jurisdiction who exercise genuine decision-making authority. Nominee directors, local administrators with no investment expertise, and professionals whose emails and call records show they routinely defer to offshore principals will not satisfy this requirement in any of the four jurisdictions.

The place layer requires physical office space under a genuine lease, not a shared-desk arrangement or a registered-address service. This does not demand a large footprint; a dedicated office accommodating two to three professionals is generally sufficient, provided it is equipped and staffed appropriately.

The process layer requires that governance decisions are documented as occurring locally. Board resolutions must reflect genuine deliberation, not rubber-stamping of decisions taken elsewhere. Investment committee minutes, risk-review records, and approval workflows must show that the local team is the decision-making locus, not merely the signatory.

The proof layer requires that all of the above is evidenced in a form that can survive regulatory scrutiny. This means retention of travel records showing physical presence at meetings, email trails that reflect local deliberation, financial records showing proportionate local expenditure, and, increasingly, responses to questionnaires sent by counterparty tax authorities under CRS exchange protocols.

Substance is no longer a compliance checkbox. It is the documented, auditable economic reality of where decisions are made, by whom, and at what cost.

Practical priorities for families reviewing structures in 2026

Families should begin with a substance audit of each intermediate entity in the ownership chain, mapping the four layers against current reality. The most common gaps are in the people and proof layers: locally engaged professionals who lack genuine authority, and governance records that are either missing or clearly retrospective. Closing these gaps requires both structural changes, such as recruiting or relocating qualified professionals, and operational changes, including revised governance protocols and document management practices.

The interaction between Pillar Two and substance rules deserves particular attention for European structures. A family that upgrades substance in Luxembourg to satisfy the ACD but holds low-taxed entities below the Luxembourg vehicle may still face a top-up tax liability at the Luxembourg level under the qualified domestic minimum top-up tax or the income inclusion rule. Modelling the consolidated effective rate across the full structure is a prerequisite for any restructuring decision.

Finally, the cost of genuine substance should be assessed against the cost of restructuring. Maintaining a two-professional office in Singapore costs roughly SGD 600,000 to SGD 900,000 annually in all-in staff and occupancy costs. For a family with SGD 200 million under management in the structure, that represents 30 to 45 basis points of AUM. That is a material but manageable cost for a structure that genuinely benefits from Singapore's treaty access and exemption regime. For a family with SGD 30 million in the structure, the same cost represents 200 to 300 basis points, which is difficult to justify on a net-return basis and may point toward a simpler structure or a different domicile. The economics of substance are now inseparable from the economics of structure design.