A company incorporated outside the UK must register with Companies House within one month of opening a UK establishment, meaning a branch or other place of business in the UK. It files form OS IN01 with a certified copy of its constitution and, where its home law requires them, its latest accounts. From then on it must report changes within 21 days, deliver accounts every year and display its name and country of incorporation at its UK premises.

What counts as a UK establishment?

Section 1044 of the Companies Act 2006 defines an overseas company as a company incorporated outside the United Kingdom. Section 1046 lets the government require such companies to register particulars, and it must do so where the company opens a branch in the UK. The detail is in the Overseas Companies Regulations 2009 (SI 2009/1801). Regulation 2 defines an establishment as a branch within the meaning of the Eleventh Company Law Directive, or a place of business that is not such a branch.

The Companies House guidance treats the test as one of physical presence. Registration is needed where the company has a place of business or branch in the UK. It is not needed for an independent agent acting for the company, or an occasional location such as a hotel used when directors visit. Partnerships, limited partnerships, unincorporated bodies and government agencies cannot register as overseas companies. The UK is treated as a single jurisdiction for this purpose.

This is a different question from the corporation tax one. Under section 5(2) of the Corporation Tax Act 2009 a non UK resident company is within corporation tax if, among other things, it trades in the UK through a permanent establishment or has a UK property business. GOV.UK warns that a company with no UK base may still need to register for corporation tax.

What has to be filed, and by when?

Regulation 4 requires the company to deliver a return and documents within one month of opening a UK establishment, and again each time it opens another. The Companies House fee for registering a UK establishment is £124 on paper. The return covers two sets of particulars.

  • The company (regulation 6): name, legal form, any home register and number, directors and secretary, the extent of their powers to represent the company and whether they act alone or jointly, whether it is a credit or financial institution, the law it is incorporated under, its accounting period where parent law requires accounts, and (unless shown in the constitution) its principal place of business or registered office, objects and issued share capital.
  • The establishment (regulation 7): its address, opening date, business carried on, any name different from the company’s, every UK resident person authorised to accept service of documents (or a statement that there is none), and every permanent representative with the extent of their authority.

Regulation 8 requires a certified copy of the constitution, meaning the charter, statutes, memorandum and articles or equivalent. Documents not in English need a certified translation. Where the company already has a UK establishment and has delivered its constitution, the new return can simply give the earlier registered number. Directors must also verify their identity with Companies House, covered in our guide to identity verification.

Which name can the company use in the UK?

The company can register its corporate name or an alternative name for UK business, which is then treated as its name in UK law. A change of name uses form OS NM01 with a £30 fee. An establishment can trade under a different name, but that name must comply with the business names rules in Part 41 of the Act. The usual restrictions on sensitive words and same as names apply, as explained in our guide to company name rules.

How are later changes reported?

Regulation 13 requires a return of any alteration in the registered particulars. For changes to the establishment, the return is due 21 days after the alteration (form OS CH01). For changes to the company itself, it is due 21 days after the date on which notice of the change could have reached the UK by post if sent with due diligence (form OS CH02). New directors, changes in powers of representation and new persons authorised to accept service all need reporting.

If the company closes the establishment, regulation 77 requires it to give notice forthwith, using form OS DS01. Until it does, the filing obligations for that establishment continue.

What accounts does the company have to file?

There are two routes, and the return states which applies.

Company type What it files Deadline
Required by parent law to prepare, audit and disclose accounts Copies of the accounting documents disclosed at home, with form OS AA01 Three months from the date they must be disclosed under parent law (regulation 34)
Not required to do so by parent law Accounts prepared under the Act as modified by the Regulations, approved by the board and signed by a director 13 months after the end of the accounting reference period (regulation 40)

For the second group, Companies House sets an accounting reference date at the month end of the date the establishment opened, which can be changed on form AA01. Filing costs £50 online or £110 on paper. Credit and financial institutions follow separate but similar rules. Missing the deadline is an offence by every director under section 451 as applied by regulation 41, with a fine up to level 5 and a daily default fine.

What must be displayed and disclosed?

Regulation 60 requires the company to display its name and country of incorporation at every UK location where it carries on business, and at the service address of each UK resident person authorised to accept service, with exceptions for premises used mainly as living accommodation. Its name must appear on all UK letters, emails, invoices, order forms and websites. Letters, order forms and websites must also give the establishment’s registered number, the country of incorporation, the home registry and number, head office, legal form, limited liability status and any winding up or insolvency.

Charges created on or after 1 October 2011 over UK property of an overseas company are no longer registered at Companies House.

How does this work in practice?

Illustration only. A company incorporated abroad opens a sales office in Manchester on 3 March 2027. Its home law requires audited accounts to be published within 12 months of its 31 December year end.

  • OS IN01, the certified constitution, a certified translation and its latest disclosed accounts must reach Companies House by 3 April 2027.
  • Its 2027 accounts must be disclosed at home by 31 December 2028, so copies are due in the UK by 31 March 2029.
  • A new UK office manager becomes the person authorised to accept service on 10 June 2027. That is a change to the establishment particulars, due by 1 July 2027.
  • If it later owns UK property, it must also join the Register of Overseas Entities, which is a separate regime.

What mistakes come up most often?

  • Opening an office and treating Companies House as an afterthought. Failing to register is an offence under regulation 11 by the company and any officer or agent who knowingly and wilfully permits it, with a fine up to level 3 and a daily default fine.
  • Confusing a UK establishment with a UK subsidiary. A subsidiary is a separate UK company with its own accounts deadlines; an establishment is part of the foreign company.
  • Assuming the 21 day clock does not apply to changes made abroad, such as a new director appointed at a home board meeting.
  • Forgetting certified translations, or certifying them by someone not on the permitted list.
  • Closing the UK office without filing OS DS01, so obligations and penalties keep running.
  • Thinking registration settles the tax position. The permanent establishment test is separate, and corporation tax registration is handled by HMRC, not Companies House.

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Sources

Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 8 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.