The controlled foreign company rules are the UK's answer to a simple manoeuvre: parking profits in a low-tax subsidiary abroad while the value is really created here. Where a foreign company is controlled from the UK, the CFC rules can apportion its "artificially diverted" profits back to UK corporate shareholders and tax them at 25% — but only where the profits pass through a deliberately narrow gateway, and only after five entity-level exemptions have failed to apply. Most foreign subsidiaries of UK groups are entirely outside the regime; the skill is in demonstrating that efficiently rather than discovering the exceptions in an enquiry.
Who the rules look at
The regime bites where a non-UK company is controlled from the UK and a UK company (with connected parties) holds an interest of at least 25%. It taxes companies, not individuals — a UK entrepreneur's personal offshore company is policed by different rules — and its target is a specific pattern: UK-controlled groups whose foreign subsidiaries earn profits out of proportion to what actually happens locally. A German trading subsidiary with a real factory and workforce is not what the rules exist for, and the architecture reflects that.
The exemptions: where most analyses end
Before any profit-by-profit analysis, five entity-level exemptions can take a subsidiary out of the regime for the period entirely:
- Exempt period — broadly the first twelve months after a foreign company comes under UK control, the grace window that lets acquisitions be restructured;
- Excluded territories — residence in a listed higher-tax jurisdiction, with modest conditions;
- Low profits — accounting or taxable profits of £500,000 or less (with non-trading income no more than £50,000): the de minimis that clears most small subsidiaries and dormant-ish entities in one line;
- Low profit margin — profits no more than 10% of operating expenditure, sheltering cost-plus service and distribution entities;
- Tax exemption — local tax of at least 75% of the equivalent UK charge, which in a 25% UK world means subsidiaries in most normal-tax countries pass automatically.
A well-run group's CFC review is mostly a spreadsheet applying these five tests entity by entity, refreshed annually — and documented, because "we assumed the exemptions applied" is not a filing position.
The gateway: what actually gets caught
For companies clearing no exemption, profits are chargeable only if they pass through specific gateway chapters — the two that matter in practice being UK-activity profits (profits attributable to significant people functions performed in the UK: the offshore IP company whose decisions are all taken in London) and non-trading finance profits (the group treasury company lending intra-group from a low-tax base). Trading profits of genuine local businesses generally do not pass through at all. Where finance profits are caught, the Chapter 9 finance company exemption can still relieve 75% — or sometimes all — of the charge on qualifying intra-group lending, which is why UK-headed groups structure treasury operations around it deliberately.
A closing chapter on that exemption's turbulent decade: the EU State aid attack on Chapter 9 — which forced HMRC to issue charging notices to dozens of groups from 2019 — ended in taxpayers' favour, with the European Court annulling the Commission's decision in 2024 and HMRC now required to reverse the notices, repay the tax with interest and restore the reliefs. Groups that paid State aid recovery should have their reversal notices and repayments reconciled; the litigation is over, and the money comes back.
Compliance and the Pillar 2 overlay
CFC positions are self-assessed: interests of 25% or more in UK-controlled foreign companies go on the CT600B supplementary pages, exemption claims included. The analysis increasingly runs alongside Pillar 2 for the largest groups — CFC tax paid in the UK is pushed down into the subsidiary's jurisdictional effective-rate calculation, so the two regimes interlock rather than duplicate — and alongside transfer pricing, which polices the same profit-location question from the pricing side.
The practical failure modes we see: acquisitions where nobody ran the CFC test on the target's foreign subsidiaries before the exempt period expired; treasury structures set up in the Chapter 9 era and never reviewed since; low-profit exemptions asserted on entities that quietly grew past £500,000; and — most commonly — no documentation at all, leaving a defensible position undefended when HMRC's international teams ask. An annual CFC memo covering the group's entities, exemptions and gateway analysis is a modest artefact that converts all of these from exposures into filing positions.
Acumon runs CFC reviews for UK-headed groups — entity mapping, exemption testing, CT600B compliance and the treasury structuring questions — through our international tax team, alongside corporation tax compliance. If your group has foreign subsidiaries and no current CFC memo, that is the gap to close before the next return.