In my previous article, I discussed why Pillar Two risk does not disappear once a transaction has completed. A buyer may identify the tax risks during due diligence, negotiate warranties and indemnities, model potential top-up tax exposure and adjust the commercial terms accordingly; however, once the acquisition has closed, the real value protection exercise begins, because the acquired business must then operate within the buyer’s wider tax control framework without creating reporting gaps, transfer pricing inconsistencies or unexpected tax leakage.

The UK’s proposed International Controlled Transactions Schedule, or ICTS, reinforces that point.

From accounting periods beginning on or after 1 January 2027, in-scope multinational groups are expected to face a new annual reporting obligation requiring detailed information on cross-border related party transactions to be provided to HMRC in a standardised format. Although the final rules and detailed HMRC guidance are still to be confirmed, the policy direction is already clear: HMRC is moving transfer pricing compliance further away from a purely narrative documentation exercise and closer to a structured, data-led compliance and risk assessment process.

That is a significant development for UK groups, inbound multinationals and acquisitive businesses.

From documentation to data

For many years, transfer pricing compliance in the UK has largely been approached through documentation: a master file, a local file, benchmarking analysis, intercompany agreements, functional analysis and supporting policy papers. Those documents remain important, and they will continue to form an essential part of any defensible transfer pricing position.

The ICTS does not replace that documentation framework, but it does change the way in which transfer pricing risk is likely to be identified and tested. HMRC will not simply be reviewing a taxpayer’s explanation of its pricing model after an enquiry has been opened; it will increasingly have access to structured information that can be compared across taxpayers, reconciled against corporation tax returns and accounts, and cross-checked against other data points such as country-by-country reporting, Pillar Two calculations, permanent establishment analysis and wider group reporting.

In practical terms, this means that the quality of the group’s transfer pricing data will become just as important as the quality of the technical analysis supporting the policy.

A group may have a theoretically defensible transfer pricing position, but if it cannot identify, classify, reconcile and explain its cross-border related party transactions consistently, the risk profile changes. The weakness may not sit in the pricing methodology itself, but in the systems, processes and governance that support the reported position.

The real question is whether the group can evidence its position

The immediate question for many groups will be whether their transfer pricing policies remain arm’s length and defensible. That is, of course, the correct starting point. However, the more difficult and often more revealing question is whether the group can produce reliable data to support those policies on an annual basis.

Can the group identify all relevant cross-border related party transactions? Can it distinguish accurately between services, royalties, financing, procurement flows, cost allocations, distribution arrangements and other controlled transactions? Can it identify the correct counterparty and jurisdiction? Can it reconcile transaction values to the statutory accounts, management accounts, ERP system and corporation tax return? Can it explain differences between the legal agreements, the accounting entries and the actual conduct of the parties? Can it identify permanent establishment dealings where those are relevant? And, perhaps most importantly, can it do this without reconstructing the position retrospectively under pressure?

These are not merely administrative questions. They go directly to the robustness of the group’s tax control framework.

Where the data is incomplete, inconsistent or difficult to reconcile, HMRC may have a natural entry point for further questions. That does not necessarily mean that the transfer pricing policy is wrong, but it may mean that the group is unable to demonstrate its position in a way that is coherent, timely and HMRC-defendable.

Why this matters in an M&A context

The ICTS is particularly relevant in a post-acquisition environment, because acquired businesses often bring with them legacy systems, informal intercompany arrangements and transfer pricing practices that were never designed to operate within a larger group compliance framework.

A target may have management charges that are booked annually through spreadsheets, intercompany agreements that no longer reflect actual conduct, royalty or service arrangements that have not been benchmarked recently, financing flows that are not fully aligned with treasury policy, or local finance teams that classify related party transactions differently from the buyer’s central tax team. In some cases, the acquired business may have cross-border dealings that were commercially understood but never properly mapped for UK tax reporting purposes.

Before the ICTS, some of these weaknesses might only have become visible if HMRC opened an enquiry or if the buyer carried out a detailed post-completion review. Under the proposed ICTS regime, however, the group may have to disclose structured information annually, making inconsistencies visible much earlier and potentially before the group has had time to correct the underlying process.

This is why transfer pricing integration should not be left until the first corporation tax return is being prepared. For acquisitive groups, ICTS readiness should become part of the Day 2 tax workstream, alongside Pillar Two readiness, legal entity rationalisation, financing review, permanent establishment analysis and tax reporting integration.

Pillar Two and ICTS are different regimes, but they expose the same weakness

Pillar Two and ICTS serve different purposes and operate through different mechanisms, but they are connected by one critical theme: both depend on the quality, consistency and ownership of tax data.

Pillar Two requires jurisdictional information, covered tax analysis, deferred tax adjustments, entity mapping, safe harbour testing and effective tax rate calculations. ICTS will require structured information on cross-border related party transactions. Both regimes require reconciliation, governance and clear accountability, and both can expose weaknesses where tax, finance, legal, treasury and the business operate in silos.

The practical risk is not limited to technical non-compliance. The more common risk may be inconsistency.

The local file may describe a transaction as a strategic management service, while the intercompany agreement refers to administrative support. The ERP system may record the same charge under a generic recharge code, while the statutory accounts present it as an operating expense. The corporation tax computation may include an adjustment, the country-by-country report may show a different allocation of profit, and the Pillar Two calculation may depend on another data set entirely.

Once the ICTS introduces structured reporting into that environment, those inconsistencies may become more visible, more difficult to explain and more likely to trigger HMRC scrutiny.

For a buyer, that is a value issue. A tax risk that was not identified, priced or operationally addressed during the transaction may become a recurring compliance burden after completion. For a CFO, it is a governance issue. For a tax director, it is a control issue. For the board, it is part of the broader discipline of managing tax risk in a data-driven environment.

The first filing period is too late to start preparing

Although the proposed commencement date may appear to give businesses time, groups should avoid treating the first ICTS filing period as the moment to begin the readiness exercise. By that stage, transactions may already have been booked, charges may already have been posted, agreements may already have been signed and local teams may already have followed historic processes that do not produce ICTS-ready data.

The more effective approach is to test readiness before the reporting obligation becomes live.

That means selecting a sample of material cross-border related party transactions and tracing them from the legal agreement to the invoice, from the invoice to the ERP system, from the ERP system to the management accounts, from the management accounts to the statutory accounts, from the statutory accounts to the tax computation and from the tax computation to the transfer pricing documentation. The question is not only whether the price is defensible, but whether the group can evidence the transaction consistently across every layer of its reporting architecture.

That exercise often reveals more than a technical memo, because it shows whether the group’s transfer pricing position is supported by operational reality.

What groups should do now

The practical response should not be panic, but structured preparation.

Groups should first determine whether they are likely to fall within the scope of the ICTS rules, taking into account the expected thresholds, the UK entities involved and the nature of their cross-border related party transactions. They should then map the relevant transaction flows, including financing, royalties, services, procurement arrangements, distribution models, cost allocations and permanent establishment dealings where applicable.

Once the transaction perimeter has been identified, the next step is to review whether the existing transfer pricing documentation reflects the current operating model, whether intercompany agreements remain accurate, whether the accounting treatment is consistent with the legal and functional analysis, and whether the relevant data can be extracted and reconciled without extensive manual reconstruction.

The ownership point is critical. ICTS should not become a year-end form completed by the tax team in isolation. Someone must own the end-to-end process: identifying the transactions, validating the counterparties, checking the numbers, reviewing the transfer pricing method, reconciling the data to the corporation tax return and maintaining an audit trail that can withstand HMRC scrutiny.

Without that ownership, the ICTS risks becoming another compliance scramble. With proper ownership, it can become a valuable control mechanism.

The commercial conclusion

Pillar Two has already changed the tax conversation for multinational groups by showing that tax risk is no longer confined to technical analysis. It is also about data, systems, governance and accountability.

The ICTS sends the same message in the transfer pricing space.

For UK groups and inbound multinationals, transfer pricing should increasingly be managed as a live control environment rather than a document prepared after the event. For buyers, ICTS readiness should form part of post-deal tax integration. For CFOs, it should sit within the wider tax risk framework. For tax teams, it is an opportunity to move from reactive compliance to proactive governance.

The groups that prepare early will be better placed to defend their transfer pricing positions, manage HMRC enquiries, reduce reconciliation issues and avoid unpleasant surprises. In a post-Pillar Two environment, where tax data is becoming more visible and more interconnected, that discipline is not simply good compliance.

It is value protection.

How Vectigalis Tax can help

Vectigalis Tax advises UK and international businesses on transfer pricing, Pillar Two readiness, cross-border structuring and post-deal tax governance.

We assist clients in identifying the tax risks that sit between technical rules and operational reality, including intercompany pricing, tax data quality, documentation, permanent establishment exposure, financing arrangements, acquisition integration and HMRC-defendable governance.

For groups preparing for the ICTS, the starting point is not simply completing a future schedule. The starting point is understanding whether the business can produce reliable, consistent and defensible transfer pricing data before the first reporting obligation arises.

If your group has UK cross-border related party transactions, has recently acquired a UK business or is preparing for post-acquisition integration, Vectigalis Tax can support you with an ICTS readiness review and a practical action plan.

Mail: info@vectigalistax.co.uk

The ICTS rules remain subject to final regulations and HMRC guidance. The precise scope, thresholds, format, submission mechanics and detailed reporting requirements may change before implementation.

This article is for general information only and does not constitute tax, legal or accounting advice. Specific advice should be taken based on the facts, group structure, accounting periods, transaction flows, documentation position and applicable UK and international tax rules.