June 30, 2026 should be circled in red at thousands of large multinational companies.
It marks the first filing due date under the Organization for Economic Cooperation and Development's Pillar Two framework — a sweeping overhaul of international tax rules that establishes a global minimum effective tax rate of 15%. For many finance and tax teams, the countdown may have started some time ago, but for others, the clock may be running down faster than they realize. How should they prepare?
Those companies best positioned for the June 30 deadline are not necessarily those with the most sophisticated tax advisors. They're the ones who started their preparation early, built centralized oversight structures, and took the operational complexity of cross-border filing seriously.
Here is what in-house tax and accounting teams need to know right now, and what they need to do to prepare for the Pillar Two deadline this year and in subsequent years.
What Pillar Two means
Pillar Two — formally known as the
The rules impose a jurisdictional-basis top-up tax: Wherever a constituent entity pays an effective tax rate below 15%, that jurisdiction's income is subject to additional tax to bring it up to the minimum. The primary mechanism for collecting this top-up tax sits within the ultimate parent entity's jurisdiction, with secondary mechanisms applying where needed.
The compliance obligations this generates are substantial. They include Pillar Two registration or notification filings in each applicable jurisdiction, the GloBE Information Return — a very detailed return covering every entity in the group across all jurisdictions — and, where applicable, top-up tax returns. A carve-out provision enables countries to continue offering tax incentives for asset- and employee-intensive business activities with genuine substance, providing some relief for operational industries like manufacturing, construction, logistics and hospitality.
The complexity that can catch companies off guard
The rationale for Pillar Two is to have a globally coordinated, harmonized corporate tax framework. The reality is considerably more complicated. Although the OECD has established a common model, individual jurisdictions have implemented it on their own timelines, with their own procedural requirements, filing formats and deadlines.
Vietnam is a case in point. For calendar-year groups the deadline for Pillar Two notification and registration was not June 2026, but within 30 days and 90 days of the ultimate parent entity's fiscal year-end — meaning January and March 2025, respectively. Companies that missed that deadline were already noncompliant before the calendar turned.
South Africa, meanwhile, only published its implementation regulations a matter of weeks ago, but still with the June 30 deadline intact. For multinationals that had put South Africa in a "wait and see" category, Pillar Two compliance has suddenly become an urgent to-do.
Belgium also presents its own administrative challenge, for example. The Pillar Two notification is notably detailed and data-intensive, and it cannot be completed via a standard online form, but requires the upload of a purpose-built Extensible Markup Language file in a format specified by the Belgian tax authority.
In some jurisdictions, the authorizations that allow service providers to file regular tax returns do not automatically apply to Pillar Two filings. Even when a service agent is already approved to act on a client's behalf, it cannot submit Pillar Two forms without obtaining a new, specific authorization. Until that is in place, the entity itself must file, even when the service provider has prepared every document. These are not edge cases; they represent the operational texture of Pillar Two compliance across a large global footprint.
The GloBE Information Return itself deserves particular attention. The GIR is perhaps one of the most complex tax returns most multinational groups will ever have encountered. It involves a comprehensive disclosure of profits, taxes, and corporate structure across every constituent entity, filed in XML format aligned to the OECD schema. It is intended to be filed once per group — typically by the ultimate parent entity in its home jurisdiction — and then exchanged with other tax authorities under Multilateral Competent Authority Agreements. However, where exchange-of-information relationships between jurisdictions are not yet in force, local filing obligations may be triggered independently. Groups that assumed a single GIR filing would discharge all their obligations may be in for an unwelcome surprise.
Five practical steps to get filing-ready
Most of the large multinationals will have already completed their Pillar Two calculations — they know whether they are in scope, whether they benefit from the transitional Country-by-Country safe harbor, and where top-up tax may be due. The challenge now is execution: converting those calculations into timely, accurate, jurisdiction-by-jurisdiction filings. Here are the steps that matter most at this stage.
1. Confirm scope and safe harbor eligibility across every jurisdiction: It is risky to assume that group-level scoping analysis tells the full story at the local level. Some entities within a group – particularly not-for-profit business lines, government-owned entities, or investment vehicles — may be excluded from Pillar Two entirely. Others may benefit from the transitional CBCR safe harbor, which can significantly reduce the compliance burden for eligible jurisdictions in the early years. Work through these determinations entity by entity and jurisdiction by jurisdiction, and document the conclusions carefully.
2. Build a master compliance calendar: The variability in local deadlines and requirements makes a centrally maintained, jurisdiction-by-jurisdiction compliance calendar essential. This tracker should capture every applicable deliverable (registrations, GIR notifications, GIR filings, top-up tax returns), the deadline in each jurisdiction, the entity responsible for filing, and the current status. For a group operating in dozens of countries, this should not be a spreadsheet exercise to be delegated to a junior team member; it requires dedicated oversight from senior compliance leadership.
3. Establish a centralized coordination hub: Pillar Two compliance cannot be managed as a collection of independent local projects. The information filed in one jurisdiction will be exchanged with tax authorities elsewhere. This means that inconsistencies between a registration filed in Belgium and a GIR filed in the U.K. will be visible to both authorities. Companies should implement a single coordinating function: one team or hub that is responsible for gathering standardized data from all relevant entities, distributing it to local teams or advisors, overseeing submissions, and ensuring every filing is consistent with others.
Whether this hub is internal or outsourced, it's essential for groups operating across more than a handful of jurisdictions. Decentralized, jurisdiction-by-jurisdiction management is simply not compatible with the consistency and accuracy that Pillar Two demands.
4. Validate technology for XML conversion and filing: The GloBE Information Return must be submitted in XML format — a technically precise file that must conform to the OECD schema, and in some jurisdictions, to local variations on that schema. Groups that have prepared their GIR data in spreadsheet form need to ensure they have access to conversion tools that can generate valid, locally compliant XML. This is not a step that can be improvised at the last minute; companies should test their conversion process now, in each jurisdiction where they will be filing, and verify that the resulting XML will be accepted by local e-filing platforms.
5. Build a defensible audit trail: Pillar Two is an annual obligation, and tax authorities have audit windows that typically extend years into the past. The team members making today's filing decisions may not be in their posts when an inquiry arrives in 2028 or 2029. Every calculation, every safe harbor determination, every scope decision and every proof of filing should be stored centrally, systematically, and with sufficient documentation to explain the logic behind the choices made. This could make the difference between an audit that resolves cleanly and one that creates significant exposure.
Centralization as a competitive advantage
Don't underestimate the value of centralization. Groups that attempt to manage Pillar Two through distributed, locally driven processes will struggle with inconsistency, missed obligations and the risk of penalties for inaccurate or late filings.
Hong Kong offers an instructive example of how the system is supposed to work. Local tax authorities have been proactively contacting entities they believe fall within scope, based on prior reporting data. This is the kind of administrative infrastructure that makes compliance manageable. But not every jurisdiction operates this way, and not receiving a letter from the tax authority is not confirmation that there is no obligation.
The most important thing at this stage is that the compliance infrastructure built for Pillar Two — the centralized hub, the compliance calendar, the standardized data flows, the audit trail — is not just for June 30. These are permanent capabilities for an annual obligation that will only grow more demanding as exchange-of-information frameworks mature and tax authorities become more sophisticated in scrutinizing GIR submissions.
Act now because the window is closing
For calendar-year groups, June 30 represents the culmination of a compliance cycle that began with fiscal year 2024. The calculations have been done and the scope has been determined. What remains is the operational execution, and this is where complexity, local divergence and the novelty of these obligations create the greatest risk of error.
If your organization has not yet completed its jurisdiction-by-jurisdiction obligation mapping, confirmed its GIR filing strategy, validated its XML conversion process, and established centralized oversight of the full submission cycle, now is the time to act. Penalties for late or inaccurate Pillar Two filings are real, and tax authorities around the world are watching closely how multinationals navigate this first filing year.
The companies that will emerge from the other side of the June 30 deadline in the strongest position will be those that treated Pillar Two compliance not as an isolated tax project, but as an enterprise-wide operational challenge. This challenge requires central coordination, consistent execution and the organizational discipline to manage complexity at scale.
