Executive summary

On 14 August 2025, the Irish tax authorities (Irish Revenue) launched their Pillar Two Hub (the website for updates and guidance in relation to Pillar Two rules in Ireland) and registration platform.

In 2023, Ireland introduced legislation giving effect to the Organization for Economic Co-operation and Development's (OECD's) Pillar Two rules under the OECD's Base Erosion and Profit Shifting (BEPS) 2.0 initiative.

The Pillar Two rules seek to ensure that in-scope¹ multinational enterprise (MNE) groups and large-scale domestic groups have a minimum effective tax rate of 15% in each jurisdiction of operation. This is achieved using a series of interlocking rules/taxes known as the Income Inclusion Rule (IIR) and Undertaxed Profits Rule (UTPR). Certain jurisdictions, including Ireland, have also opted to implement a Qualified Domestic Top Up Tax² (QDTT).

The Pillar Two rules also require in-scope groups to comply with a series of registration, filing and payment obligations. Irish Revenue has now launched the Pillar Two Hub and registration platform to enable applicable taxpayers to satisfy these obligations.

To comply with the forthcoming 31 December 2025 deadline (for groups using the calendar year as their fiscal year), taxpayers will need to take action as follows:

• Prepare the relevant details of each constituent entity (plus Joint Ventures (JV), JV affiliates etc.) located in Ireland.
• Assess which tax each entity is liable for with regard to 2024 (i.e., for IIR and/or QDTT) based on its status as a relevant parent entity and/or other chargeable entity.
• If there are multiple Irish-located entities, decide which entity will be the designated local entity (DLE) (i.e., the entity that files the Top-Up Tax Information Return (TIR) or identifies for Irish Revenue the foreign entity that will file the Global anti-Base Erosion (GloBE) Information Return (GIR)).
• If there are multiple Irish-located entities, determine whether a QDTT Group will be formed and, if so, which entity will be the QDTT Group filer.

Further details are set out below.

Registration

Entities³ located in Ireland that are within the scope of the rules must register for the relevant Pillar Two taxes (i.e., IIR, UTPR, QDTT) within 12 months from the end of the first fiscal year for which the entity is subject to the relevant tax. For example, an entity with a fiscal year ending on or before 31 December 2024 that is subject to the IIR and/or QDTT for 2024 must register for these taxes by 31 December 2025.⁴

Details must also be provided as to whether the registering entity is electing to become a member of a QDTT Group and/or a UTPR Group and, if so, whether it is appointed as the QDTT/UTPR Group Filer.

Entities must also notify Irish Revenue as to whether a TIR will be filed in Ireland or whether the obligation will be met by a designated filing entity in another jurisdiction.

Registration should be completed via Irish Revenue's Revenue Online Service (ROS). Entities that qualify for the OECD's Transitional Country-by-Country Safe Harbour (TCSH) are also required to register for Pillar Two taxes. Failure to register could lead to a penalty of €10k.

Once registered, entities must notify Revenue of any change in the information provided, including if the entity ceases to be subject to the relevant tax, within 12 months of the end of the fiscal year in which the change occurred.

Payment and filing obligations

The relevant Pillar Two returns (i.e., QDTT/IIR/UTPR returns and self-assessments) are due for filing, along with any payments due, within 15 months from the end of the fiscal year (extended to 18 months if the fiscal year is a Transition Year⁵).

Simplified tax filing and payment arrangements are available if all Irish entities of a group elect to form a QDTT Group as part of the registration process. A similar process is available for entities within the scope of the UTPR.

A TIR (or notification of filer)⁶ must also be filed within 15 months of the end of the fiscal year (extended to 18 months if the fiscal year is a Transition Year). If there are multiple Irish-located entities, a DLE may be appointed to file a TIR with Irish Revenue on behalf of all of the Irish entities⁷ or prepare and deliver the notification of filer to Irish Revenue with details of the entity filing the GIR.⁸

The feature on ROS allowing taxpayers to file the relevant Pillar Two tax returns is expected to be available in 2026.

Revenue correspondence

Irish Revenue reportedly has started issuing Pillar Two Registration Letters to in-scope groups as part of a phased approach, with Phase 1 focusing on Irish Ultimate Parent Entities of groups likely to be in scope of Pillar Two top-up taxes. These letters are a prompt for action, advising taxpayers that the registration functionality is now live on ROS and outlining compliance obligations and means of complying. Recipients of the letters who believe they are not within scope may respond via the MyEnquiries function on ROS, outlining why they believe they are not within the scope of the rules.

Next steps

Action should be taken now by in-scope groups to assess and identify the Pillar Two registration requirements for each of their Irish entities. This is particularly relevant for calendar-year taxpayers that are required to register no later than 31 December 2025.

If a group contains multiple Irish entities, the entities should consider whether to form a QDTT Group/UTPR Group and which entity should be the relevant filing entity for the group in advance of the registration deadlines. Groups also need to consider which entity will file the TIR, to include an analysis of GIR Multilateral Competent Authority Agreement coverage and how this information will be exchanged.

Affected taxpayers should contact their tax advisors to discuss their Pillar Two registration and compliance obligations ahead of the relevant deadline.