The global minimum tax is moving into a new phase: countries are beginning a coordinated review of the domestic laws they have adopted to implement it. The process is intended to check whether those national rules line up with the shared international framework—and to identify differences that could create uncertainty for governments and multinational companies.
The rules generally apply to multinational groups with consolidated annual revenue of at least €750 million in two of the previous four years. They require in-scope groups to calculate an effective tax rate in each jurisdiction where they operate. If the rate on relevant profits falls below 15%, top-up tax may be due under rules that determine which jurisdiction has the right to collect it.
What The Review Covers
The review will examine national legislation for the three main parts of the framework: the Income Inclusion Rule, which can impose top-up tax at a parent-company level; the Undertaxed Profits Rule, which serves as a backstop; and the Qualified Domestic Minimum Top-up Tax, which allows a country to collect top-up tax on low-taxed income within its own borders.
Reviewers will also assess whether domestic rules meet the conditions for related safe harbours. These matter because a jurisdiction’s status can affect how other countries apply the framework to the same multinational group. Where reviewers identify inconsistencies, the process is designed to produce recommendations for countries to address them.
This is a review of how countries have written and applied the agreed rules—not a fresh negotiation of the 15% minimum rate. It also does not mean every difference in national tax systems will disappear. The central question is whether a country’s implementing rules qualify under the shared framework.
Why Companies Should Pay Attention
For businesses, the review could influence where top-up tax is ultimately collected and which calculations or filings are required. A domestic minimum tax that meets the framework’s standards can affect whether another jurisdiction may seek to collect tax on the same low-taxed income. Companies will want to track the status of the rules in every country where they operate, particularly when those rules interact across a parent company, subsidiaries and local entities.
The review also comes as the framework evolves. Recent international guidance includes simplifications and safe harbours, while countries continue to update their own laws and administrative systems. A group’s calculation may therefore depend on more than the headline tax rate: local rules, the treatment of tax incentives, accounting data, filing requirements and the timing of legislative changes can all matter.
What To Monitor
Tax and finance teams should keep a jurisdiction-by-jurisdiction record of enacted rules, effective dates, qualification status and open legislative changes. They should also check how local minimum taxes interact with parent-level rules and backstop rules, and whether incentives or other tax attributes receive the treatment expected under the current guidance.
Reporting readiness remains another practical priority. Groups may need to gather consistent financial and tax data across entities, reconcile those figures with local requirements and prepare for information exchange between tax authorities. Changes to reporting formats and filing procedures make it important to confirm which requirements apply for each reporting year.
The review is expected to clarify how the common framework operates in practice, but it will not remove every source of uncertainty at once. Companies should distinguish between rules already in force, changes proposed or enacted locally, and review recommendations that may lead to future amendments.
MarketMind Insight
The review puts implementation quality at the center of the global minimum tax story. For multinationals, the immediate task is to understand how each jurisdiction’s rules fit together—and to keep calculations and reporting flexible as countries respond to the findings. The 15% rate is the framework’s headline; its practical effect will depend on how national laws translate that shared standard into tax obligations across a company’s footprint.
