The OECD Pillar Two framework establishes a global minimum tax regime which applies to multinational groups with consolidated revenue over €750 million. For those that exceed this threshold, the rules aim to ensure income is taxed at a global minimum effective tax rate of 15% on a jurisdiction-by-jurisdiction basis. The 30 June 2026 Pillar Two information return deadline is now imminent for large groups, and those impacted need to urgently ensure they are ready for reporting.

UK adoption of the rules

The UK adoption of the Pillar Two rules introduces two new taxes: Multinational Top-up Tax (MTT) and Domestic Top-up Tax (DTT). Both were originally introduced in the Finance Act in 2023, with further amendments made in 2024 and 2025, with the aim of aligning UK legislation with OECD guidance.

A group is within the scope of the additional taxes if the consolidated group revenue exceeds €750 million in any two of the previous four periods. The rules apply to accounting periods beginning on or after 31 December 2023.

The new taxes

MTT is charged on UK parent members where a subsidiary is located in a non-UK jurisdiction and the profits arising in that jurisdiction are taxed below the 15% minimum effective tax rate.

DTT applies the rules of MTT to the UK operations of in-scope groups, and to certain wholly domestic UK groups and standalone UK entities meeting the revenue threshold, to ensure that UK profits are taxed at a minimum of 15%.

Reporting

If a group is within the scope of the new taxes, a group member must register with HMRC within six months of the end of the accounting period in which it becomes qualifying. The UK filing company is required to submit a self-assessment return and an information return to HMRC for each qualifying period. For groups with a 31 December 2024 year end, the first information return must be submitted by 30 June 2026.

It is important to note that filing obligations apply even where safe harbours have been elected and no top-up tax is due.

Additionally, where the GloBE Information Return is being filed centrally in another jurisdiction, UK entities will still be required to file a UK self-assessment return and an Overseas Return Notification indicating the jurisdiction in which the GloBE Information Return has been filed.

The OECD Side-by-Side package

On 5 January 2026, the OECD Inclusive Framework released the Side-by-Side (SbS) package, formalising the political agreement reached by the G7 in June 2025. The centrepiece of the package is the SbS Safe Harbour. Where a group's ultimate parent entity is located in a jurisdiction with a Qualified SbS Regime, the group may elect to deem its MTT top-up tax to be zero.

Currently, the United States is the only jurisdiction recognised as having a Qualified SbS Regime. However, the safe harbour applies only to fiscal years beginning on or after 1 January 2026, therefore US-headed groups must continue to apply the full GloBE Model Rules for the preceding periods, and full Pillar Two reporting will be required for the upcoming 30 June 2026 deadline.

How we can help

The implementation of Pillar Two brings significant compliance, calculation, and data-gathering requirements for in-scope multinational groups and the UK members of those groups. Our Pillar Two service offering is built around a tiered approach, enabling clients to select the level of support that best fits their internal capability and the position adopted by the wider group. Our support can range from filing only to fully outsourced support.

Our support typically covers the following areas.

1. Scope assessment and registration:

   We assess whether the group is within the scope of the UK rules, advise on the operation of the €750 million revenue threshold across the relevant testing periods, and support UK registration with HMRC.

2. Safe harbour analysis:

   We undertake jurisdiction-by-jurisdiction safe harbour analysis.

3. GloBE calculations:

   We can prepare the group calculations in full or undertake a detailed review of calculations prepared by clients or by overseas advisors. We use a market-leading Pillar Two software platform to support both calculation and filings. Ours clients are granted direct access to the calculation portal and templates, with the Buzzacott team having review access.

4. UK and international filings:

   We can prepare and submit the UK MTT and DTT self-assessment return, the GloBE Information Return or, where the GloBE Information Return is being filed in another jurisdiction, the Overseas Return Notification. Where the engagement requires international Domestic Minimum Top-up Tax or GloBE Information Return filings outside the UK, we can also support with the international filings.

Get in touch

If you’d like to speak to one of our experts for support with your Pillar Two obligations ahead of the 30 June 2026 deadline, download our guide or get in touch by filling out the form below.