Specialist Accountants for US and UK Businesses: GILTI, FDII and Global Tax Compliance
Introduction
Running a group across the United States and the United Kingdom is no longer just about filing accounts in two places. It now means dealing with GILTI, FDII, controlled foreign corporation reporting, transfer pricing, and global minimum tax rules that can affect tax cost, compliance workload, and commercial decision-making. That is why more companies now seek specialist accountants for US and UK businesses before a routine filing issue becomes a structural tax problem.
This matters even more in 2026, as US international tax reporting remains highly technical while the UK continues to develop its Pillar Two and transfer pricing frameworks. The IRS still requires US shareholders of certain foreign corporations to calculate GILTI on Form 8992, and domestic corporations still use Form 8993 for the section 250 deduction tied to FDII and GILTI. http://www.irs.gov/forms-pubs/about-form-8992 http://www.irs.gov/forms-pubs/about-form-8993 (Internal Revenue Service)
This guide is written for founders, directors, CFOs, investors, and finance teams with US and UK operations. It explains what these rules mean in practice, why the risks are both commercial and tax-driven, and how specialist accountants for US and UK businesses can help build a more resilient cross-border structure.
Why GILTI, FDII, and global tax compliance now belong in one conversation
A few years ago, many groups treated US international tax, UK corporation tax, and OECD-driven global compliance as separate subjects. That approach no longer works. A business can have a technically correct US filing and still create UK transfer pricing exposure or future Pillar Two friction.
The reason is simple. Modern international tax rules interact. GILTI affects how US shareholders measure foreign subsidiary income. FDII affects how some US corporations think about qualifying foreign-derived income. UK multinational top-up tax rules affect how large groups monitor effective tax rates and reporting systems. HMRC’s updated collection on Domestic Top-up Tax and Multinational Top-up Tax shows that this remains an active compliance area, and the collection was updated in July 2025. http://www.gov.uk/government/collections/multinational-top-up-tax-and-domestic-top-up-tax (GOV.UK)
That is why specialist accountants for US and UK businesses add value far beyond form preparation. Good advisers connect the rules into one planning conversation. They help management understand not just what must be filed, but what the structure is actually doing to cash tax, reporting risk, and group governance.
What GILTI means in practical business terms
GILTI stands for Global Intangible Low-Taxed Income, but many business owners misunderstand it because the name suggests a narrower scope than the actual rule. In practice, it is a US international tax inclusion regime that can apply when a US shareholder owns controlled foreign corporations and must calculate an inclusion under section 951A. The IRS states this directly in its Form 8992 materials. http://www.irs.gov/forms-pubs/about-form-8992 (Internal Revenue Service)
For US and UK businesses, this often means a US parent with a UK subsidiary, a US entrepreneur owning a UK trading company, or a US group holding non-US operating entities through one or more foreign corporations. The tax issue is not just whether GILTI exists. The real issue is how the group’s legal structure, earnings profile, and local tax burden shape the result.
This is where many businesses get caught out. They assume GILTI is a year-end tax calculation. In reality, it is also a planning signal. It forces a group to ask where income arises, where functions sit, how profits are allocated, and whether the group’s current design still matches its commercial model.
Why FDII still matters
FDII is often less widely understood than GILTI, but it remains important. The IRS says domestic corporations use Form 8993 to calculate the section 250 deduction for FDII and GILTI. The December 2025 instructions also state that, before the scheduled reduction, section 250 generally allows a deduction equal to 37.5 percent of FDII plus 50 percent of GILTI, with lower percentages applying thereafter. http://www.irs.gov/forms-pubs/about-form-8993 (Internal Revenue Service)
For businesses selling goods or services from a US corporation to foreign customers, FDII can materially affect effective tax modeling. It can influence where companies hold functions, how they contract with foreign clients, and how they measure the tax consequences of serving international markets from the United States.
That does not mean every business should redesign around FDII. It does mean that groups with real export activity should not ignore it. This is one of the reasons businesses engage specialist accountants for US and UK businesses rather than relying on general domestic compliance support.
Why Form 5471 remains one of the biggest pressure points
Many business owners worry most about tax calculations, but the biggest operational risk often sits in information reporting. Form 5471 remains one of the most important compliance returns for certain US persons with interests in certain foreign corporations. The IRS continues to identify it as the core information return in this area. http://www.irs.gov/forms-pubs/about-form-5471 (Internal Revenue Service)
The challenge is not only technical. It is operational. Form 5471 requires good ownership records, timely financial data, intercompany detail, and clarity on the role of each foreign entity. If the group’s accounting systems do not produce this data cleanly, the tax filing becomes slow, risky, and expensive.
That is why specialist accountants for US and UK businesses focus on data flow as much as tax law. They help groups organize entity maps, intercompany ledgers, local reporting packs, and filing calendars so the annual process becomes controlled rather than reactive.
How the UK side has changed the conversation
Cross-border business owners sometimes think the heavy technical burden sits only on the US side. That is no longer true. The UK now has an active Pillar Two framework, and HMRC guidance confirms that Multinational Top-up Tax and Domestic Top-up Tax apply for accounting periods beginning on or after 31 December 2023. HMRC also issued further amendments in late 2025 and updated them again in January 2026. http://www.gov.uk/government/publications/further-amendments-to-multinational-top-up-tax-and-domestic-top-up-tax http://www.gov.uk/government/publications/further-amendments-to-multinational-top-up-tax-and-domestic-top-up-tax/pillar-2-further-amendments-to-multinational-top-up-tax-and-domestic-top-up-tax (GOV.UK)
That means businesses with UK group entities cannot focus solely on the US return. They need to understand whether the broader group could fall into top-up tax reporting, future notification obligations, or systems changes. HMRC’s March 2026 software guidance makes clear that businesses or their agents need compatible commercial software to submit UK Pillar Two returns and related notifications. http://www.gov.uk/guidance/choose-the-right-software-for-pillar-2-top-up-taxes (GOV.UK)
Even groups below the threshold should still pay attention. Investors, acquirers, and larger counterparties increasingly expect finance teams to know whether the structure is ready for this environment.
UK transfer pricing reform matters more now.
The UK is not standing still on transfer pricing either. HMRC’s 2025 to 2026 reform materials show that the government moved forward with changes to transfer pricing, permanent establishment, and diverted profits tax rules, with changes generally taking effect for chargeable periods beginning on or after 1 January 2026. HMRC’s International Manual now includes updated material on the reform package. http://www.gov.uk/government/consultations/reform-of-transfer-pricing-permanent-establishment-and-diverted-profits-tax/outcome/reform-of-transfer-pricing-permanent-establishment-and-diverted-profits-tax-summary-of-responses http://www.gov.uk/hmrc-internal-manuals/international-manual/intm414010 (GOV.UK)
This matters because transfer pricing is no longer just a documentation exercise. It now sits at the center of international tax control. If a group cannot clearly support how profits are allocated between the US and UK, that weakness affects multiple areas at once: corporation tax, GILTI inputs, top-up tax risk, audit exposure, and transaction readiness.
That is why specialist accountants for US and UK businesses should be reviewing pricing policy, legal agreements, management substance, and real operational conduct together, not as separate files.
Pillar Two is not only a problem for the very largest groups.
It is true that the OECD’s GloBE framework targets large multinational groups, generally those meeting the EUR 750 million revenue threshold in at least two of the four preceding fiscal years. The OECD continues to describe that threshold in its Pillar Two administrative guidance. http://www.oecd.org/content/dam/oecd/en/topics/policy-sub-issues/global-minimum-tax/agreed-administrative-guidance-for-the-pillar-two-globe-rules.pdf (GOV.UK)
But it would be a mistake for mid-market groups to switch off. A group might sit below the threshold today and still need better systems tomorrow. It may plan to scale, acquire, raise capital, or become part of a larger multinational group. If the underlying entity structure and intercompany framework are weak, future compliance becomes much harder.
That is one of the strongest commercial arguments for using specialist accountants for US and UK businesses. They do not just answer whether you file today. They help you avoid building tomorrow’s problem into today’s structure.
The business impact for founders, directors, and CFOs
These rules do not affect tax teams alone. They affect the commercial core of the business.
For founders, the biggest issue is often that the original structure was built for speed rather than durability. A company may have started with a simple UK or US entity and then added foreign customers, overseas staff, intercompany service charges, and new subsidiaries without ever redesigning the tax framework.
For CFOs, the issue is control. Can the finance team produce accurate data for GILTI, Form 5471, transfer pricing, and future top-up tax analysis without turning every close process into a crisis? If not, the group has an operating problem, not just a filing problem.
For investors, the concern is hidden leakage. Weak international tax governance can reduce enterprise value, slow diligence, and increase deal friction. In that context, proactive advisory work often costs far less than fixing historic exposure during a transaction.
What good cross-border tax support should actually look like
A strong advisory process should start with the structure itself. Who owns what? Which entity contracts with customers? Where are key people located? Which company develops value? How do cash, royalties, services, and financing move across the group?
From there, the work should move into reporting and control. That includes Form 5471 scope, GILTI modelling, section 250 analysis, UK tax review, transfer pricing support, and governance around deadlines and data collection.
That is where specialist accountants for US and UK businesses stand apart. They understand that the technical answer only matters if the business can operate it in real life. The best cross-border tax work is not just legally correct. It is also practical, scalable, and understandable to management.
Why this matters now
The international tax environment is becoming more, not less, connected. The IRS continues to require detailed GILTI and section 250 reporting. HMRC continues to develop the UK’s Pillar Two framework and transfer pricing reforms. That means businesses cannot rely on old international tax assumptions and expect them to hold up in 2026. http://www.irs.gov/forms-pubs/about-form-8992 http://www.gov.uk/government/collections/multinational-top-up-tax-and-domestic-top-up-tax (Internal Revenue Service)
The groups that respond early usually gain more than compliance. They gain cleaner structures, better information systems, stronger investor readiness, and fewer surprises. That is what businesses are really buying when they engage specialist accountants for US and UK businesses.
Conclusion
GILTI, FDII, Form 5471, UK top-up tax rules, and transfer pricing reform all point in the same direction. Cross-border groups need joined-up oversight. Separate local compliance work is no longer enough for businesses that operate seriously across the United States and the United Kingdom.
The strongest approach is proactive, commercial, and structured. It looks at how the business actually operates, then builds a tax and reporting framework around that reality. That is how companies reduce friction, manage risk, and protect value as they grow.
If your business needs a clearer strategy for GILTI, FDII, Form 5471, Pillar Two readiness, or UK transfer pricing reform, now is the right moment to review the structure before the next filing cycle creates more complexity. Contact hello@jungletax.co.uk or call 0333 880 7974
FAQs
What is GILTI for a US and UK business group?GILTI is a US international tax inclusion that can apply to certain US shareholders of controlled foreign corporations.
Does FDII still matter in 2026?Yes. The IRS still maintains Form 8993 for the section 250 deduction, and current instructions confirm that the deduction rules continue with reduced percentages after the earlier period.
Do UK groups need to care about Pillar Two now?Yes,
HMRC says Multinational Top-up Tax and Domestic Top-up Tax apply for accounting periods beginning on or after 31 December 2023, and updated 2026 guidance shows reporting systems remain active. (GOV.UK)
Yes. HMRC’s reform materials say the government moved forward with transfer pricing reforms in the Finance Bill 2025 to 2026, with changes generally taking effect for chargeable periods beginning on or after 1 January 2026. (GOV.UK)
Why is Form 5471 such a big risk area?Because it is not just a tax form, it depends on accurate ownership, financial, and intercompany data across the group. If the underlying data is weak, the filing becomes slow and risky. (Internal Revenue Service)
Why use cross-border specialists instead of separate local firms?Because the real risk often sits in the interaction between the rules. A joined-up team is more likely to integrate GILTI, FDII, Form 5471, UK top-up tax, and transfer pricing into a single workable strategy.