Mauritius updates QDMTT regulations for 2026.

Mauritius has published detailed rules for how its Qualified Domestic Minimum Top-up Tax (QDMTT), in force since mid-2025, is actually calculated and administered. The regulations are accompanied by a separate Finance Act 2026 amendment to the underlying charging provisions. The Mauritius Revenue Authority has also confirmed 30 September 2026 as the new filing and payment deadline for the earliest cohorts of in-scope groups.

Businesses with Mauritius entities forming part of a large multinational group should take note, since the updated rules directly shape how much tax is payable locally, the deadlines for filing returns and the penalties that now apply if compliance slips.

What the regulations set out

The Income Tax (QDMTT) Regulations 2026 were proclaimed on 8 August 2026. They set out the methodology for computing the effective tax rate of Mauritius resident constituent entities, establish procedures for applying the top-up tax due and clarify how the QDMTT should be administered day to day. They also identify persons excluded from the regime, giving groups more clarity over its scope.

The regulations are designed to produce substantially the same outcome as the OECD’s Global Anti-Base Erosion Model Rules, Commentary and Administrative Guidance, ensuring the Mauritius regime qualifies internationally as a recognised domestic minimum tax.

Two features stand out for groups assessing their exposure. The first is the Substance-Based Income Exclusion, covering both payroll and tangible asset carve outs, allowing groups to exclude income linked to genuine local substance from the top-up tax calculation. The second is a transitional Country-by-Country Reporting safe harbour, offering potential relief for eligible groups during the early years of the regime.

Amendments under the Finance Act 2026

The Finance Act 2026, assented on 12 August 2026, amended several QDMTT charging sections in the Income Tax Act, with most changes applying retrospectively. Among them, the penalty for late payment of QDMTT has been reduced from 5% to 2.5%, and the window to submit an amended return has been extended from two years to three. Groups that modelled their Mauritius exposure before these changes should revisit those calculations.

Filing deadlines by fiscal year cohort

The earliest cohort of in-scope groups, those whose fiscal year ended between 1 January and 31 May 2025, must file and pay QDMTT by the extended deadline of 30 September 2026, with no penalties or interest provided returns and payment are made by that date.

Groups with a 30 June 2025 fiscal year-end also fall due on 30 September 2026 under the standard rule of 15 months after fiscal year-end. Other cohorts follow their own deadlines on the same rolling, 15-month basis. Compliance sits with a single designated Mauritius entity responsible for filing the group’s QDMTT return, though all local group entities remain jointly liable for the tax itself.

What this means going forward

Mauritius joins a growing list of jurisdictions operationalising Pillar Two through a domestic minimum tax rather than ceding the taxing right elsewhere. Multinational groups with Mauritius operations should model their effective tax rate under the new methodology and check whether the substance based exclusions or transitional safe harbour reduce their exposure.

Given the pace of change and the retrospective effect of several provisions, businesses with a Mauritius presence forming part of a large multinational group should seek professional advice to confirm their obligations under the new regime.