Luxembourg Pillar Two: registration, GIR and top-up tax return deadlines

Country reference

• Country: Luxembourg (planned expansion country)
• Authorities: Administration des contributions directes (ACD); Ministry of Finance
• Topic: Minimum effective taxation (Pillar Two) compliance
• Key date: First deadline 30 June 2026; then 15 months after year end
• Law: Amended Law of 22 December 2023; Law of 19 December 2025 on exchange of top-up tax information returns

Who must do what

• Registration: constituent entities, joint ventures and their affiliates located in Luxembourg.
• GloBE information return (GIR): all Luxembourg constituent entities, unless filed by the ultimate parent or a designated filer abroad and notified to the ACD.
• Top-up tax return: entities liable under the income inclusion rule, the UTPR or the national top-up tax.

Deadlines

• The first deadline for these procedures was 30 June 2026.
• In general, filings are due 15 months after the end of the tax year, or 18 months for the first year.
• Changes and deregistration must be reported within 15 months after the year end.
• A May 2026 regulation lists the jurisdictions with an eligible agreement for exchanging the GIR.

How to file

• All filings go through MyGuichet.lu with LuxTrust or an eID.
• The GIR is uploaded as an XML file; registration and returns can be pre-filled from XML.

Penalties

• EUR 5,000 for failing to register, update or deregister, or for wrong information.
• EUR 5,000 for failing to notify the ACD of the GIR filer.
• Up to EUR 250,000 for a late, incomplete or inaccurate GIR, and up to EUR 300,000 in some cases.
• The ACD assesses top-up tax where no correct return is filed.

What to do now

• Confirm every Luxembourg entity is registered and the filing entity is notified.
• For calendar-year 2025, plan GIR and return work well before the next 15-month deadline.
• US-parented groups: check how the OECD side-by-side arrangement affects your Luxembourg filings.

Our take

Luxembourg holding and financing companies of large groups are squarely in scope. The fines are fixed and high, so treat registration as a priority even where no top-up tax is due.