Reverse hybrid rules and the Luxembourg SCSp: Article 168quater LIR after the 2025 circular

The Luxembourg reverse hybrid rule of Article 168quater LIR has been in force since tax year 2022 and is the most consequential anti-hybrid mechanism that any Luxembourg fund sponsor structuring through a transparent partnership has to live with.¹² Where the rule applies, it converts a normally tax-transparent SCSp or SCS into an entity-level Luxembourg corporate income taxpayer on the income that would otherwise escape both Luxembourg tax and the tax system of its non-resident investors. The fund’s headline neutrality at Luxembourg level is preserved only if the rule does not trigger, or if a carve-out applies.

The carve-out matters. For most Luxembourg fund structures, the relevant safe harbour is the collective investment vehicle exemption in paragraph 2 of Article 168quater LIR. Until the summer of 2025, the practical application of that carve-out was unclear in the boundary cases that come up most often in private equity and venture capital structures — unregulated SCSps managed by an authorised AIFM, master-feeder configurations and concentrated investor bases. Circular L.I.R. n° 168quater/2 of 12 August 2025 issued by the Luxembourg tax administration consolidated that practice and gave sponsors a workable reading of the three CIV conditions.³

For sponsors structuring a Luxembourg SCSp, the reverse hybrid analysis is now part of the standard structuring conversation, alongside the AIFM regime, the GP setup and, where the wrapper applies, the RAIF framework. The reverse hybrid rule does not change the architecture of these structures, but it imposes a discipline on the cap table, the investor base and the documentation file that the structuring decisions must respect from the outset.

1. The ATAD 2 framework and Article 168quater LIR

Council Directive (EU) 2017/952, known as ATAD 2, was adopted on 29 May 2017 and required Member States to neutralise hybrid mismatches that result in deduction without inclusion, double deduction or double non-taxation outcomes.⁴ The directive included a specific set of rules for reverse hybrids — entities that the Member State of establishment treats as transparent but that a non-resident investor treats as opaque — designed to capture the slice of income that would otherwise fall through the cracks between the two jurisdictions.

Luxembourg transposed the reverse hybrid rule through Article 168quater of the Luxembourg income tax law, applicable to fiscal years beginning on or after 1 January 2022.² The rule sits inside the corporate income tax book of the LIR and operates as a recharacterisation. Where its conditions are met, the partnership ceases to be read for direct tax purposes solely through its partners and becomes a separate Luxembourg corporate income taxpayer on the income captured by the rule.

This is the single most significant change to the Luxembourg direct tax treatment of the SCS and SCSp since the partnership tax regime was redesigned in the 2013 reform. The transparent entity tax profile that made these forms attractive for international fund structures remains the default. Article 168quater is the targeted exception that applies when the structure interacts with non-resident investors in a way that produces the mismatch the directive was designed to address.

2. The mechanism: when the rule triggers

Article 168quater LIR triggers when three cumulative conditions are met.² The Luxembourg entity must be a partnership treated as transparent for Luxembourg direct tax purposes — typically an SCS or an SCSp, although the rule is drafted on the basis of the tax classification rather than the legal form. Associated non-resident entities must hold, directly or indirectly, 50% or more of the voting rights, capital interests or profit entitlements in the partnership. Those associated non-resident entities must treat the partnership as a taxable person in their home jurisdiction, that is, as fiscally opaque rather than transparent.

When the three conditions are met, the partnership becomes liable to Luxembourg corporate income tax on its net income, but only to the extent that the income is not otherwise taxed under Luxembourg domestic tax law or the law of any other jurisdiction. The “otherwise taxed” check is the bracket that prevents double taxation. Income that is taxed in the hands of a Luxembourg-resident partner under transparency, or that is taxed in the hands of a non-resident partner whose home state treats the partnership as transparent, is outside the perimeter of the rule.

The rule is therefore narrower than it might appear on a first reading. It captures only the slice of income attributable to the associated non-resident entities that treat the partnership as opaque, only to the extent that this income is not taxed elsewhere. For a Luxembourg fund whose investor base is mixed, with some investors treating the SCSp as transparent and others treating it as opaque, only the latter slice is within the perimeter.

3. The 50% associated-investor test

The 50% threshold is read by reference to associated non-resident entities, taken in aggregate. Two technical points matter in practice.

The 50% is computed by reference to voting rights, capital interests or profit entitlements. Any of the three measures triggers the test if it crosses the threshold. The wording is deliberately broad. A cap table that splits voting rights and profit entitlements differently across investor classes — for example a structure where the GP holds voting rights and limited partners hold profit entitlements — must be analysed by reference to each measure separately. Crossing the threshold on any single one of them is sufficient.

The “associated entities” notion follows the general ATAD 2 affiliation rules transposed into Luxembourg tax law. Investors are associated when they share ownership thresholds, control or family relationships that bring them within the perimeter set by the directive. Two unrelated non-resident investors holding 30% each will not be aggregated, even though their combined interest is 60%, unless they are associated within the meaning of the rule. Two affiliates of the same group sharing 60% in aggregate will be aggregated and trigger the test.

The test is performed on a continuous basis. A change in the investor base over the life of the fund — secondary transactions, redemptions, new commitments at successor closings, GP removals — can move the cap table across the threshold. The reverse hybrid file is therefore monitored on the same cadence as the AIFM Annex IV reporting and the LP register, rather than as a one-off check at fund formation.

4. The CIV carve-out and the August 2025 circular

Paragraph 2 of Article 168quater LIR contains the collective investment vehicle exemption.² A CIV is defined as an investment fund or vehicle that is widely held, holds a diversified portfolio of securities and is subject to investor-protection regulation in the country in which it is established. The three conditions are cumulative.

The circular treats three categories as CIVs by their nature: UCIs governed by the Law of 17 December 2010, SIFs governed by the Law of 13 February 2007 and RAIFs governed by the Law of 23 July 2016. A SICAR is not part of that list and must therefore be tested against the statutory conditions, including portfolio diversification.³

Outside the listed UCI, SIF and RAIF perimeter, the CIV qualification has to be assessed against the three conditions as clarified by Circular L.I.R. n° 168quater/2 of 12 August 2025. The circular addresses the evidence relevant to each condition, including the position of an unregulated SCSp managed by an authorised AIFM, without turning the AIFM appointment into a substitute for the other two tests.³

The circular’s main contribution is structural. It reads the three CIV conditions as one functional definition of a properly run fund, rather than as a checklist of formal labels, and it offers presumptions and grace periods for the practical situations in which the conditions are most often debated.

5. The widely-held condition

The widely-held condition is the most operationally sensitive of the three. The circular formulates it as a requirement of broad investor participation, presumed met where no single investor ultimately holds or controls, directly or indirectly, more than 25% of the capital or voting rights of the fund.³ The 25% threshold is therefore the practical anchor for the analysis, although it operates as a presumption rather than as a hard rule, and a fund that crosses it can still be widely held on the basis of other indicators.

The circular addresses two recurring concerns. The first is the launch and wind-down phases of a fund’s life. A new fund that is still ramping up its investor base, and a mature fund that is winding down toward a small group of remaining LPs, are unlikely to meet the 25% threshold at every point in time. The circular allows a grace period of up to 36 months from authorisation or establishment during which the widely-held condition is not breached if it is reasonable to consider that it will be met within that window. The same logic applies in mirror image to the wind-down phase.

The second is the related-investor analysis. Investors are treated as related where they meet ownership thresholds of 50% or more, where they share family relationships, or where they form part of the same control structure. A single institutional investor that subscribes through several feeders or affiliates is therefore treated as a single investor for the 25% test. The expected use case — a club deal among truly unrelated co-investors — is preserved, but the structuring of feeders and parallel funds inside a single fund family must be designed with this aggregation in mind.

6. The diversified-portfolio condition

The circular reads the diversified-portfolio condition broadly.³ Securities for the purposes of the carve-out include shares, partnership interests, units in other funds, beneficiary shares, bonds and other debt claims, bank deposits, and certain derivatives where the underlying assets are themselves securities. The definition is therefore wide enough to accommodate the asset classes typically held by Luxembourg PE, VC, private debt, infrastructure and fund-of-funds vehicles.

Diversification is read in line with the SIF framework. Single-issuer concentration is generally limited to no more than 30% of the fund’s assets. The standard SIF concentration analysis applies, with the usual flexibility for fund-of-funds positions and for short-term liquidity holdings. A fund that concentrates above the SIF threshold without a documented justification will struggle to demonstrate the diversified-portfolio condition.

The condition is more flexible than it might seem at first reading for fund strategies whose deployment trajectory naturally produces concentration. A PE fund that holds a small number of large-ticket positions can still qualify if the concentration is the result of a defined deployment plan and if the fund’s overall investment policy is consistent with the SIF-style diversification framework. The circular’s reading rewards a coherent investment policy and a documented deployment trail more than it rewards a rigid statistical balance at every point in time.

7. The investor-protection condition

The investor-protection condition is the most consequential clarification of the August 2025 circular for Luxembourg PE and VC sponsors. The condition is met where the fund is under CSSF prudential supervision or where it is managed by an AIFM authorised under the AIFMD.³

The two limbs are alternatives for the investor-protection condition. A product under CSSF prudential supervision can rely on that supervision for this limb. An unregulated SCSp may rely on management by an authorised AIFM where the circular’s conditions are met. For a vehicle outside the automatic UCI, SIF and RAIF list, the widely-held and diversified-portfolio conditions still require their own analysis.

The practical implication is narrower. Management by an authorised AIFM can support the investor-protection limb for an unregulated SCSp; it does not establish that the vehicle is widely held or that its portfolio is diversified. A registered or sub-threshold AIFM does not provide that same basis under this limb, so the CIV position must be assessed from the complete legal and factual file.

Where the investor-protection limb relies on the AIFM appointment, a change in AIFM during the life of the fund requires the authorisation status and continuity of the appointment to be checked. A move to a sub-threshold AIFM, or a period without the relevant appointment, requires that limb and therefore the overall CIV analysis to be revisited.

8. Practical implications for SCSp structuring

The reverse hybrid rule and the CIV carve-out together set a structuring discipline that is now built into the standard Luxembourg fund file. Three points come back regularly during structuring.

The investor base must be analysed against the 50% associated-investor test. Funds with a concentrated US LP base — where the US investors typically check the box and treat the SCSp as opaque — are the structures most directly exposed. Funds with a broad European and Asian institutional LP base, where most investors treat the SCSp as transparent, sit further from the rule. Master-feeder configurations that route US investors through a separate feeder vehicle can move the perimeter of the rule by isolating the opaque-treating cohort.

The CIV qualification must be analysed from the structure’s outset. UCIs under the 2010 Law, SIFs and RAIFs fall within the circular’s listed perimeter. A SICAR or unregulated SCSp must instead establish the investor-spread, portfolio-diversification and investor-protection conditions in light of its legal form and strategy. Testing those elements only at the first year-end leaves a material classification question unresolved during the launch period.

The CIV qualification rests on broad investor participation, a diversified portfolio and investor-protection regulation. The LP register and related-investor analysis concern the first condition, the investment policy and actual deployment concern the second, and the AIFM’s status concerns the third.

9. Changes that affect the qualification

Successor closings, secondary transactions and LP removals can move the cap table across the 25% widely-held threshold or the 50% associated-investor threshold. The 36-month grace period offers a buffer during the launch phase but does not suspend those tests.

Strategy concentration during deployment can change the diversified-portfolio analysis. This may occur where a PE fund holds few positions, a credit fund concentrates on few borrowers or a real-estate fund narrows toward a single market.

A move to a registered AIFM or a period without an AIFM appointment affects the investor-protection condition and reopens the reverse-hybrid analysis for income earned during that period.

10. The interaction with broader tax compliance

The reverse hybrid file connects with the rest of the SCSp’s tax compliance workstream. Where the CIV carve-out applies, the partnership remains tax-transparent for direct tax purposes and continues to file and report on that basis. Where the carve-out does not apply and the rule triggers, the partnership becomes a corporate income tax payer on the captured slice of income and the tax compliance file moves accordingly.

The interaction with the SOPARFI holding layer and with single-deal SPVs sitting below the partnership is relevant. The reverse hybrid rule applies to the SCSp itself, not to the corporate companies it holds. Income earned at SOPARFI level is taxed at SOPARFI level under the standard Luxembourg corporate framework, regardless of the reverse hybrid analysis at SCSp level. The interaction is therefore at the level of the partnership’s income and its allocation to investors, not at the level of the underlying portfolio companies.

The reverse-hybrid outcome connects the partnership’s tax return, AIFM information and investor reporting. A legislative, administrative or factual change can alter the analysis for a later period.

Conclusion

Article 168quater LIR can recharacterise a Luxembourg transparent partnership as a corporate income taxpayer for the captured income. The CIV carve-out depends on broad investor participation, portfolio diversification and investor-protection regulation. The remaining anti-hybrid rules address different mismatch outcomes through deduction denial or income inclusion.⁴

Footnotes

1. According to the Luxembourg legislator, the reverse hybrid rule of Article 168quater of the Luxembourg income tax law was introduced into Luxembourg tax law to implement Article 9a of Council Directive (EU) 2016/1164 as amended by Council Directive (EU) 2017/952, and is applicable to fiscal years beginning on or after 1 January 2022. ↩

2. Law of 4 December 1967 on income tax (LIR), as amended, including Article 168quater on the reverse hybrid rule and its CIV carve-out in paragraph 2. ↩ ↩² ↩³ ↩⁴

3. According to the Luxembourg tax administration, Circular L.I.R. n° 168quater/2 of 12 August 2025 clarifies the three conditions of the CIV carve-out — broad investor participation, diversified portfolio of securities and investor-protection regulation — and confirms that an authorised AIFM under the AIFMD satisfies the investor-protection condition for unregulated SCSps. ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

4. Council Directive (EU) 2017/952 of 29 May 2017 amending Directive (EU) 2016/1164 as regards hybrid mismatches with third countries (ATAD 2), the EU base of the Luxembourg reverse hybrid rule. ↩ ↩²