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On 22 October 2025, the Belgian Federal Public Service Finance published Circular 2025/C/68 (Dutch / French), providing clarification on the Belgian Act of 19 December 2023 introducing a minimum tax of 15% for multinational enterprises and large domestic groups.
This circular, which is extensive (247 pages), discusses the provisions of the Global Minimum Tax Act. It situates the new rules within the OECD BEPS 2.0/Pillar 2 framework and EU Directive 2022/2523, clarifies the main definitions and calculation methods, and describes the functioning of the top-up taxes such as the Qualified Domestic Minimum Top-up Tax (QDMTT), the Income Inclusion Rule (IIR), and the Undertaxed Profits Rule (UTPR). The circular explicitly emphasises that the interpretations contained therein apply solely to the implementation of the Minimum Tax Act itself and may not automatically be transposed to the ordinary corporate income tax or other tax legislation.
Circular 2025/C/68 as a practical guide aligned with OECD and EU guidelines
The circular does not introduce new insights or major surprises. Its content closely reflects what was already known from international sources. It is primarily based on the OECD commentary (Consolidated Commentary on the GloBE Model Rules, April 2024), the OECD Pillar Two Administrative Guidance, and the FAQ accompanying the EU Pillar 2 Directive.
In other words, the Belgian tax authorities adhere to the OECD and EU framework. Accordingly, the circular largely confirms and summarises already published rules and clarifications. It serves primarily as a practical guide summarising and contextualising known principles in a Belgian framework, without introducing unexpected deviations or additional insights.
In a previous Tax Insight concerning the Belgian Pillar 2 Act, we already outlined the main principles.
Key (New) elements and points of attention
Although the circular does not introduce groundbreaking new rules, it clearly sets out the key points and obligations arising from the new minimum tax. Notable elements include:
- Scope and definitions: Explanation of which groups fall within the rules; multinational groups and large domestic groups with a consolidated annual turnover ≥ EUR 750 million.
The circular defines core concepts such as group entity, MNE group, ultimate parent entity, etc., in line with the law and OECD definitions. Certain ambiguities in the law are addressed; for instance, clarification is provided as to which entities qualify as constituent entities. - Computation of qualifying income and effective taxation: The methodology for determining GloBE income and adjusted taxes per jurisdiction is explained in detail.
The circular describes how to move from the commercial accounts to the tax-adjusted base, and how the effective tax rate (ETR) per jurisdiction is calculated according to OECD rules. Exclusions*, adjustments, and carve-outs (e.g. the Substance-Based Income Exclusion or “SBIE”) are clarified.
The circular, for example, confirms the treatment of certain CFC regimes: the concept of blended CFC tax regimes (including the US GILTI) is referenced with reference to Article 67/1 of the Act and the OECD commentary. Such references illustrate Belgium’s adherence to international interpretations in complex scenarios. - Computation and allocation of the top-up tax:
The rules for determining the top-up tax amounts are explained. A jurisdiction first has the right to apply a domestic top-up tax (QDMTT) on low-taxed profits.
If it does not, the charge shifts to the group level via the IIR (borne by the ultimate parent entity) and finally via the UTPR as a backstop. The circular sets out this cascading mechanism in line with the OECD model.
Special cases such as restructurings, acquisitions, and transitional regimes are also covered. - Practical obligations: Compliance obligations are addressed, including the notification requirement for in-scope groups (see our earlier Tax Insight on this topic), the filing of the GloBE Information Return (GIR), and the declaration for the domestic top-up tax (see our Tax Insight on the QDMTT return). While the circular itself does not detail the technical aspects of filing, it confirms who must or may file (e.g. the filing group entity) and the statutory deadlines**. It also mentions the joint and several liability of group entities for Belgian top-up taxes.
In short, the circular serves as a comprehensive guide in which the Belgian tax authorities systematically explain the new minimum tax. For in-scope businesses, it confirms the applicable rules and provides useful references to the official OECD commentary and examples.
*To reduce the administrative burden during the initial years, temporary “safe harbours” have been introduced. These allow a simplified assessment — without complex calculations — of whether there is a risk of low-taxed income in a given jurisdiction. The assessment is primarily based on data from a qualified Country-by-Country report (CbCR) of the group (to be published for financial years starting on or after 22 June 2024). If a group can rely on one of the three safe harbours for a given country, no top-up tax is due for that jurisdiction. This enables the group to avoid the complexity of calculating qualifying income and covered taxes.
Note: The "once out, always out" principle applies, if a jurisdiction does not qualify for a safe harbour in one year, it cannot do so in subsequent years either.
**There will always be a filing obligation, regardless of whether the group is subject to a top-up tax in Belgium or can rely on one of the safe harbours.
What Is missing from the Circular?
It is noteworthy that certain aspects are not covered. The scope of the circular is expressly limited to Title II, Chapters 1–10, (partly) 12 and 13 of the Act. Consequently, Chapter 11 of the Act, “Assessment and Collection of the Minimum Tax”, is not addressed. In practice, this means there is no clarification on how the minimum tax will be assessed and collected. Details concerning the assessment process, payment, and administrative handling of the top-up tax are omitted — as expected, since the Belgian tax authorities intend to address these procedural aspects at a later stage. Given the approaching deadlines (within 11 months after the end of the fiscal year – i.e. by 30 November 2025 for groups on a calendar-year basis, covering the financial year 2024 (the first year Pillar 2 is in effect)) and the need for additional clarification on the practical QDMTT compliance requirements (return filing, etc.), the tax authorities have decided to grant an extension until 30 June 2026 for filing all returns concerning the domestic top-up tax whose statutory filing deadline falls before 30 June 2026 (announcement by the Federal Public Service Finance dated 17 November 2025). Practical guidance and technical documentation on the filing procedure will be communicated at a later stage.
Furthermore, the circular does not refer to the proposed side-by-side solution of the United States.
This G7-level proposal, discussed in 2025, aims to accommodate US groups subject to their own minimum tax regime (GILTI). The solution would exclude US-based multinationals from the IIR and UTPR under Pillar 2, in light of existing US minimum tax rules.
Although this proposal was made public in mid-2025, the circular contains no reference to or analysis of its potential impact, focusing instead on the Belgian legislation currently in force.
Finally, the circular does not mention the new draft bill (Parliamentary Documents, Chamber, Session 2024–2025, No. 56-1070), tabled in October 2025, which proposes technical amendments to the Act of 19 December 2023. This bill codifies key procedural aspects omitted from the original Act, dated 17 October 2025. Among other things, it introduces a formal assessment system for the minimum tax (allowing the tax authorities to issue one joint assessment notice covering the QDMTT, IIR, and UTPR for all Belgian group entities) and creates the concept of a general representative for groups with multiple Belgian entities to fulfil the group’s obligations. It also proposes to shorten the statute of limitations for the minimum tax from 10 to 6 years and extend joint liability to certain associated entities (e.g. joint ventures) that fall under the QDMTT. These points are absent from the current circular, as they are subject to future legislative amendment. The circular addresses only the Act as approved at the end of 2023, while the draft Bill remains pending.
Conclusion: The new circular on the minimum tax primarily consolidates existing knowledge and international guidance within a Belgian context. It confirms the implementation of Pillar 2 in Belgium but does not introduce any new or unexpected interpretations. However, it provides clear and useful guidance on the calculation and application of the top-up tax and on taxpayer responsibilities. Topics such as the actual assessment and collection process, certain international exceptions (such as the US side-by-side solution), and forthcoming technical legislative amendments remain outside the scope of this circular and will need to be monitored through future guidance or legislative updates.
Step-by-step approach
The calculation of the various top-up taxes follows these steps:
- Definition of the scope, jurisdictions, and entities falling under Pillar 2;
- Verification of the potential application of one of the temporary safe harbours. If none apply, proceed to steps 3 to 6;
- Calculation of the qualifying income or loss per jurisdiction (taking into account the Substance-Based Income Exclusion (SBIE), whereby part of the result may be excluded from the top-up tax calculation);
- Determination of the covered taxes per jurisdiction;
- Computation of the Effective Tax Rate (ETR) per jurisdiction;
- Application of the appropriate top-up tax (the domestic top-up tax, IIR, or UTPR).
If you would like to receive additional information on this matter or require tax assistance, the RSM Belgium Tax team is at your disposal via [email protected].
