Executive summary

On 6 January 2026, Luxembourg released the forms for Pillar Two registration and filing of the local tax return as well as the Global anti-Base Erosion (GloBE) Information Return (GIR) on its online platform MyGuichet. Entities falling within the scope of the amended law of 22 December 2023, regarding minimum effective taxation for multinational enterprise groups and large-scale domestic groups (the Pillar Two Law), and subject to its provisions in the 2024 calendar year are required to meet all related compliance obligations by 30 June 2026.

Detailed discussion

Registration and notification

In accordance with the Pillar Two Law, every Luxembourg constituent entity (CE) belonging to an in-scope group is required to use the registration procedure on MyGuichet. Though much of the information requested is administrative and straightforward, certain sections will require decision-making. Amendments to the registration must be submitted as necessary. Deregistration must be completed using the same process.

The registration process also requires identifying the GIR filing entity in case the group decides to centralize GIR filings with a single Luxembourg CE or the Ultimate Parent Entity (UPE) or a Designated Filing Entity in a jurisdiction that has a Qualifying Competent Authority Agreement in effect.

The information required by the form includes:

• The CE's name and tax identification number (TIN)
• The name of the group to which the entity belongs
• The name, jurisdiction and TIN of the UPE
• The fiscal year in which the group became subject to the Pillar Two rules and the year the entity joined the group (if later than when the rules first applied to the group)
• Contact person details
• The name, jurisdiction and TIN of the entity filing the GIR
• For the following items, the CE may appoint designated entities, in which case the name and TIN of the designated entity must indicated:
  
  • Filing and paying the top-up tax under the Qualified Domestic Minimum Top-up Tax (QDMTT)
  • Filing and paying the top-up tax under the Undertaxed Profit Rule (UTPR)

Joint ventures or joint venture subsidiaries within the meaning of Pillar Two Law that are located in Luxembourg are also required to register.

Luxembourg local top-up tax return

The Luxembourg local top-up tax return form is available online via MyGuichet and as an XML file, covering top-up taxes under the Income Inclusion Rule (IIR), UTPR and QDMTT. It requires disclosure of general details such as the entity's name, legal form, address and TIN, along with information pertaining to the group, the legal representative and the tax compliance service provider. The form requires that the amounts payable for each of the three taxes be indicated but does not require detailed calculations.

Pillar Two is a self-assessment tax. Taxes must be paid within one month of filing the return. Upon completion of the form, a reference number is generated that needs to be provided with the payment.

For the QDMTT and UTPR, a designated local entity (umbrella entity) may be appointed to file the top-up tax return and make related payments.

Globe Information Return

The GIR may be submitted either in Luxembourg or in a foreign jurisdiction if Luxembourg has entered into an information exchange agreement with that jurisdiction. The GIR form is based on the Grand-ducal regulation from 19 December 2025, which implemented the standardized Top-up Tax Information return in line with the European Union Directive on Administrative Cooperation (DAC 9). The form closely aligns with the Organisation for Economic Co-operation and Development's (OECD's) GIR template released in July 2023 and updated in January 2025. (For background, see EY Global Tax Alert, OECD releases new documents on GloBE Information Return, dated 21 January 2025.)

Implications

For groups in scope of Pillar Two for calendar year 2024, the deadline for registration and filing their GIR and top-up tax return is 30 June 2026. Groups therefore should get ready to collect the relevant data to be able to meet their compliance obligations. In case of non-filing or late filing, penalties may arise.