The Companies House number, explained
What a UK company registration number looks like, what it proves, and how fast you can get one.
A UK company registration number (CRN) is the identifier Companies House assigns when a company is incorporated. Per Companies House's own developer forum, all company numbers are 8 characters long: companies formed in England and Wales get 8 digits, while companies registered in Scotland carry an "SC" prefix and companies in Northern Ireland carry an "NI" prefix, each followed by 6 digits (other prefixes exist for specific entity types, such as credit unions or Scottish charitable incorporated organisations).
The number appears on the certificate of incorporation issued once registration completes — the document that "confirms the company legally exists and shows the company number and date of formation." Registering online costs £100 and is usually processed within 24 hours; registering by post with form IN01 costs £124 and takes 8 to 10 days. Every grant, tender and registry lookup that asks for a "company number" in the UK means this one.
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Last reviewed 2026-09-25. Rules and figures change — follow the links above to confirm anything you plan to rely on.