Companies House is the executive agency of the British Government that maintains the register of companies, employs the company registrars and is responsible for incorporating all forms of companies in the United Kingdom.

Prior to 1844, no central company register existed and companies could only be incorporated through letters patent and legislation. At the time, few incorporated companies existed; between 1801 and 1844, only about 100 companies were incorporated. The Joint Stock Companies Act 1844 created a centralised register of companies, enabled incorporation by registration, and established the office of the registrar; the Joint Stock Companies Act 1856 mandated separate registrars for each of the three UK jurisdictions. Initially just a brand, Companies House became an executive agency in 1988.

All public limited, private limited, private unlimited, chartered and some other companies are incorporated and registered with Companies House. The agency also registers limited partnerships, while most other enterprises fall under the purview of the Financial Conduct Authority. All limited companies (including subsidiary, small and inactive) must file annual financial statements with Companies House, all of which are public records. The agency is also responsible for dissolving companies.

From 2016, Companies House operated under the authority of the Department for Business, Energy and Industrial Strategy. This then became the Department for Business and Trade from 7 February 2023 following a Machinery of Government change initiated by Prime Minister Rishi Sunak. The current chief executive is Louise Smyth, who is also registrar for England and Wales. The agency, as well as British company law in general, is governed by the Companies Act 2006. As of May 2025,^[update] Companies House maintains records of over 5.44 million active companies, including over 5.11 million private limited companies and over 4,000 public limited companies.

Prior to 1844, companies could only be incorporated through grant of a royal charter, by private act of Parliament, or, from 1834, by letters patent. Few companies were incorporated, with only approximately 100 companies being incorporated by private act between 1801 and 1844. At this time, no central register of companies was in existence.

The origins of Companies House date back to 1844, the year the Joint Stock Companies Act received royal assent, enabling companies to be incorporated by registration for the first time. The Act created the office of the Registrar of Joint Stock Companies to maintain the register of companies, which was publicly accessible. It was hoped by MPs of the day that a publicly accessible central company register would help to protect the public from fraud. All companies, irrespective of their method of incorporation, were obliged to register within three months of the commencement of the Act.

The Act provided for two types of company registration: provisional, and complete. The filing requirements for complete registration were more extensive than those for provisional registration. Given that there was no requirement for companies granted a certificate of provisional registration to submit the remaining information in order to become completely registered, the Act was not hugely successful as many of its provisions applied only to completely registered companies.

The Joint Stock Companies Act 1844 applied only to England and Wales, and Ireland; it did not apply to Scotland.