OS IN01 at Seventeen: The Overseas Companies Register Britain Still Runs Alongside ROE — and the Branch-or-Subsidiary Question After Brexit

Most readers of this publication can now recite, more or less, the shape of the Register of Overseas Entities. It was introduced under the Economic Crime (Transparency and Enforcement) Act 2022, applies to foreign entities owning qualifying interests in UK land, and now sits on around 30,000 live registrations. We have written about it at length.

Far fewer readers can describe — without checking — how Britain registers a German GmbH that opens a sales office in Slough, a Delaware Inc. that runs a London engineering team, or an Irish DAC that operates a permanent UK branch. That register exists. It has existed, in its current form, since 1 October 2009. It is housed inside Companies House. It is searchable on the same service as a domestic limited company. And it is governed by a body of law — Part 34 of the Companies Act 2006 and the Overseas Companies Regulations 2009 (SI 2009/1801) — that the Economic Crime and Corporate Transparency Act 2024 has, so far, almost entirely left alone.

This is the OS-prefix filing world: OS IN01, OS AA01, OS DS01, OS CC01. It is one of the most useful pieces of the UK register for serious due diligence, and one of the least understood. With the Part 34 regime now in its seventeenth year and ECCTA reshaping almost everything else around it, it is worth setting out what the regime actually does, where it sits next to ROE, and what the asymmetry now means.

What Part 34 actually requires

The core obligation is in section 1046 of the Companies Act 2006: an overseas company that opens a UK establishment must register that establishment with the registrar within one month. "UK establishment" is defined by regulation 2 of SI 2009/1801 as a branch within the meaning of the Eleventh Company Law Directive, or a place of business that is not a branch. That deliberately broad phrasing collapsed an older Companies Act 1985 distinction — between "branches" (Schedule 21A) and "places of business" (Schedule 21D) — into a single registration regime.

A "place of business" can be very modest. The case law that came up under the 1985 Act, particularly Re Oriel Ltd [1985] BCC 99,444 and South India Shipping v Export-Import Bank of Korea [1985] 1 WLR 585, treated even a small, leased liaison office capable of binding the company as sufficient. Companies House guidance still tracks that threshold: a representative office that does no more than collect market information is unlikely to bite; one that takes orders or signs agreements almost certainly does.

Once registered, the establishment files into Companies House using the OS forms:

The accounts position is the part most often misread. Under regulation 31 of SI 2009/1801 an overseas company whose parent-law disclosure regime is judged broadly equivalent — most EEA states, the US, Canada, Japan, Australia — files its home-state accounts, in the home-state currency, on the home-state cycle. A company from a non-equivalent jurisdiction must instead prepare modified accounts to UK content rules. There is no consolidation requirement specific to the UK establishment, and no separate UK profit-and-loss line for the branch.

The volumes Britain rarely cites

The register is small relative to the domestic company stock — roughly 5.4 million live entities at the last published Companies House count — but is not trivial. On the current public register, the population of registered overseas companies with at least one live UK establishment sits in the region of 12,000–14,000. That number has been broadly stable for several years, having drifted down from a 2018 peak above 16,000.

The rough composition is also stable:

• Around 55 per cent of registered overseas companies are incorporated in EEA states, with Ireland, Germany, the Netherlands, France and Luxembourg consistently the five largest source jurisdictions.
• Around 20 per cent are incorporated in the United States, weighted heavily toward Delaware.
• Channel Islands, Isle of Man and Gibraltar together account for around 8 per cent.
• The remainder is long-tailed across more than a hundred jurisdictions.

The Companies House Free Company Data Product publishes the entire OS slice each month, and any practitioner running director-network or beneficial-ownership work against UK trade can pull it for granular slicing. It is, in our view, one of the most under-used datasets the registrar publishes.

Why Brexit changed the shape, not the size

The headline expectation in 2020 was a collapse in EEA-branch registrations as companies converted to UK subsidiaries to preserve services passports, employment relationships, and contractual continuity. That collapse arrived for a slim band of regulated sectors — most visibly financial services, where the Temporary Permissions Regime largely funnelled EEA firms toward authorised UK subsidiaries — but it was nowhere near the wholesale rebasing some commentators predicted.

What actually happened was a quieter rebalancing. The volume of EEA-incorporated overseas companies with live UK establishments fell by roughly a fifth between 2019 and 2024, but the absolute number of UK establishments of non-EEA companies edged up over the same period, particularly from the United States and the Republic of Ireland (which from a UK-registration perspective is now non-domestic but enjoys most of the practical advantages of proximity). The net effect: a slightly smaller register, more US-weighted, with the EEA share down but still dominant.

The practical Brexit story for the register is therefore less about exit and more about three smaller shifts:

1. Reduced equivalence shortcuts. Pre-Brexit, EEA-incorporated overseas companies enjoyed the most permissive accounts regime under regulation 31. They retain a generous regime, but the political question of equivalence is now bilateral rather than automatic, and changes in either direction would be felt here first.
2. Increased scrutiny on "shell branches." The Treasury and HMRC have shown more appetite to test whether a UK establishment is a genuine permanent establishment for corporation-tax purposes versus merely a name on the register. The diagnostic gap between Companies House registration and HMRC PE status has tightened.
3. A consultative drift toward branch reporting. The FRC and BEIS's successor department have circulated, without yet legislating, proposals for additional disclosure of UK branch activity within group accounts. Nothing is yet in force.

ROE and the OS regime: two registers, often conflated

Because both registers were active by mid-2022 and both concern foreign entities, the two are routinely confused — including in legal commentary that should know better. They overlap only at the edges.

The practical implication for due diligence is the one most often missed: a foreign company can appear on the ROE because it owns a London office building, and separately be required to appear in the Part 34 register because it operates that office as a UK establishment. Compliance with one says nothing about compliance with the other. Conversely, neither register catches a foreign company that does business in the UK only through travelling staff, distributors or a UK-incorporated subsidiary it owns from offshore.

The ECCTA gap

What is most striking about the OS regime, eighteen months into the ECCTA reform programme, is how little of it has been touched.

• Directors of overseas companies are not subject to the new identity-verification regime under section 1110A CA 2006 (as inserted by ECCTA). The verification duty bites on directors of UK-incorporated companies and on PSCs registered in the UK; it does not extend to directors of a Delaware Inc. registered as an overseas company with a London branch.
• The appropriate-address rule (section 1141 CA 2006, as amended) applies to UK companies' registered offices. Overseas company UK-establishment service addresses are governed by a separate provision in SI 2009/1801 reg 7, which has not been brought into alignment.
• The lawful-purpose statement now required of UK companies at incorporation and on each confirmation statement has no Part 34 counterpart. There is no annual confirmation-statement-equivalent for the OS register at all — the accounts cycle is the only mandatory annual touchpoint.
• The fee structure for the OS regime was uplifted in May 2024 alongside the wider Companies House fees reform (OS IN01 rose from £20 to £71; OS AA01 from £30 to £62; OS DS01 from £10 to £33), but the underlying cost-recovery model that funds ECCTA enforcement on the domestic side has no obvious counterpart in how the OS register is supervised.

The consequence is awkward. A small UK private limited company with a £10,000 turnover now sits inside a verification, suppression, lawful-purpose and software-only-filing regime more onerous than the one applied to a US-listed parent operating a London office through an overseas-company registration. There is no defensible policy reason for that asymmetry; there is a practical reason, which is that Part 34 was not on the ECCTA drafting list.

Where this leaves practitioners

For anyone running serious counterparty diligence on a UK trading entity, three working rules now apply.

First, a search of the domestic register alone systematically under-captures foreign corporate presence. Pulling the OS slice — by company-type filter on the Companies House service, or by direct download of the Free Company Data Product — should be standard.

Second, ROE and Part 34 are not substitutes. If a target is a foreign entity touching UK land or operations, both registers should be checked. Inconsistencies between them — and there are many — are themselves diagnostic.

Third, the absence of identity-verification on overseas-company directors is now a material gap in the UK transparency regime. It will not last indefinitely. The most likely vehicle is a statutory instrument under the ECCTA delegated powers, possibly bundled with the next round of Part 34 amendment. For now, the practical workaround is the same one used in the years before ECCTA: parent-jurisdiction registries, sanctions-screening, and where appropriate the trust-and-corporate-services-provider supervision regime in the jurisdiction of incorporation.

The OS register has been quietly doing its work since 2009. Seventeen years in, it deserves more attention than it gets — not least because it is the last large corner of the Companies House estate that the current reform programme has chosen, so far, to leave alone.