Luxembourg Pillar Two filing obligations

At a glance

The Luxembourg Tax Authorities (LTA) have made Luxembourg Pillar Two compliance fully operational with the launch of dedicated online procedures on 6 January 2026. These procedures allow for the registration of Luxembourg constituent entities (CEs), the submission of the GloBE Information Return (GIR) where Luxembourg acts as the filing jurisdiction, and the filing of the Top-Up Tax Return. In scope Pillar Two groups with financial years starting on or after 31 December 2023 are required to comply, with calendar year end groups facing a 30 June 2026 deadline. All filings must be completed electronically via MyGuichet.lu. This milestone underscores the shift from Pillar Two a future-orientated reporting concept to an active local compliance regime that must be managed in parallel with global reporting obligations.

A closer look
 

Registration, rectification, update of registration, and deregistration

Luxembourg CEs that are members of multinational enterprise (MNE) groups or large-scale domestic groups are subject to the registration, rectification of registration, update of registration, and deregistration obligations set out in Article 49 of the Luxembourg Pillar Two law.

Registration is required for the fiscal period in which a group first becomes subject to Pillar Two, or in which a Luxembourg CE joins a group already within scope. The registration deadline is 15 months following the end of the relevant fiscal year, extended to 18 months for the transition year.

As part of the registration process, each Luxembourg CE must provide, where applicable, the following information:

1. Identity and tax identification number (TIN) of the CE
2. Name of the MNE or large-scale domestic group
3. Identity, TIN and jurisdiction of the Ultimate Parent Entity (UPE)
4. Fiscal year from which the group falls within the scope of Pillar Two
5. Fiscal year in which the entity joined the group, if later than the year in which the group entered the scope
6. Fiscal year for which the procedure applies
7. Identity of the designated group filing entity
8. Identity of the designated local filing entity
9. Identity of the designated (umbrella) paying entity for UTPR purposes
10. Identity of the designated (umbrella) paying entity for QDMTT purposes
11. Name and contact details of the individual responsible for the registration.

Any subsequent changes to the information provided during registration must be communicated to the LTA, through the same procedure, within 15 months following the end of the fiscal year in which the change occurred.

Deregistration is required where a group ceases to fall within the scope of Pillar Two, or where the entity no longer qualifies as a Luxembourg CE (e.g. following liquidation or a change in scope). Deregistration must be completed within 15 months following the end of the fiscal year and is carried out through the same online procedure.

The filing obligations also apply, with necessary adaptations, to Luxembourg joint ventures and joint venture affiliated entities.

Filing of the GIR and related notification

Under Article 50 of the Luxembourg Pillar Two law, Luxembourg CEs are required to file a GIR within 15 months following the end of the fiscal year, extended to 18 months for the transition year.

A Luxembourg CE may be exempted from filing the GIR if it is submitted by the UPE, or a designated filing entity located in a jurisdiction that has an eligible competent authority agreement with Luxembourg. In such cases, the Luxembourg CE must notify the LTA of the identity and jurisdiction of the entity filing the return.

While a separate online procedure exists for filing the GIR, there is no standalone procedure for the GIR notification. Instead, the notification is embedded in the registration process. This suggests that the notification is generally a one-off requirement, with any subsequent changes to the designated GIR filing entity to be communicated via the notification of change mechanism mentioned above.

Accordingly, where the GIR is filed outside Luxembourg, the registration process must include the designation of the entity responsible for filing the GIR. When making this designation, groups should consider factors such as whether the filing jurisdiction has implemented Pillar Two rules, whether it has signed the Multilateral Competent Authority Agreement, and whether adequate data protection and information sharing safeguards are in place.

The registration process also allows for the designation of a Luxembourg CE responsible for either filing the GIR (where applicable) or notifying the LTA of the group entity filing the GIR.

Declaration and payment of top-up taxes

Under Article 51 of the Luxembourg Pillar Two law, Luxembourg parent entities (UPE or Intermediate Parent Entity or Partially Owned Parent Entity) and/or designated umbrella entities are required to declare and pay the Income Inclusion Rule (IIR) tax, the Undertaxed Profits Rule (UTPR) tax, and any Qualified Domestic Minimum Top-up Tax (QDMTT). The relevant entity must submit a Top-up Tax return specifying the amounts of each tax.

In this regard, it should be noted that the Luxembourg parent entities that would be responsible for any IIR payments would automatically need to file a Top-up Tax Return. Furthermore, the designated UTPR entity and QDMTT paying entity will also be required to file a Top-up Tax Return., Therefore, the Top-up Tax Return could be due by several Luxembourg CEs.

Based on the current format of the form, a Top-up Tax Return must be submitted even where no top-up tax liability arises. 

The Top-up Tax Return must be filed within 15 months following the end of the fiscal year (extended to 18 months for the transition year). Payment of any tax due is required within one month of filing.

Electronic filing

Currently, all three forms must be submitted electronically via the MyGuichet.lu portal, using the applicable electronic signature method. The Pillar Two Registration form and the Top-up Tax Return may be completed either manually or by uploading an xml file. In contrast, the GIR can only be completed via xml upload.

The Luxembourg Pillar Two legislation also provides a structured legal framework for the automatic exchange of GIRs filed in Luxembourg, in line with the OECD global minimum tax framework and the EU DAC 9 rules. Further details are discussed in our previous tax alert Luxembourg adopts national legislation on DAC9 and implements January 2025 OECD guidelines | Deloitte Luxembourg  issued in December 2025.

Penalties

Luxembourg CEs that fail to register or deregister within the prescribed deadlines, or that submit incomplete or inaccurate registration information, may be subject to a penalty of EUR 5,000.

Late, incomplete, or incorrect submissions of the GIR may result in penalties of up to EUR 250,000. The statute of limitations for audits and enforcement is 10 years.