--- title: "Company number" summary: "A company number is the identifier a register assigns to a company at incorporation, and it is unique only within the register that issued it — never within a country and never globally." canonical_url: https://entitybind.com/glossary/company-number last_updated: 2026-10-15 copy: full --- # Company number > A company number is the identifier a register assigns to a company at incorporation, and it is unique only within the register that issued it — never within a country and never globally. Canonical page: https://entitybind.com/glossary/company-number Last updated: 2026-10-15 Glossary · Identifiers ## How to read this The definition as the field writes it comes first, weaknesses and all. What Entity Bind does about it comes last, in its own paragraph, so you can take one without the other. [Filed under identifiers](https://entitybind.com/glossary#identifiers). By [James Rooney](https://entitybind.com/about), founder of Entity Bind · Last revised 15 October 2026 ## What company number means A company number is the identifier a register gives a company when it incorporates. Companies House issues eight-character numbers, optionally with a letter prefix that encodes the jurisdiction or company type. Other registers use entirely different shapes. The number is authoritative for the register that assigned it and means nothing outside it. The most common and most expensive mistake in company data is treating 'company number plus country' as a unique key. It is not: many jurisdictions run more than one register, German numbers are qualified by the court that holds them, and several countries operate parallel number spaces for tax, statistics and incorporation. A record whose number is stored without its issuing authority has lost information that cannot be recovered by inspection, because the shapes overlap. The second common mistake is normalising the number as if it were an integer. Stripping leading zeros or a letter prefix creates collisions with other schemes, and a six-digit remainder can look like a completely different kind of reference. Entity Bind stores registration numbers scoped to their issuing authority, checks register shape rather than string equality, and treats conflicting authority-scoped numbers as a decisive non-match rather than as a weak negative signal. Name uniqueness in the register is measured before any claim is made about name matching: on Companies House's 5,464,811 live companies, 99.53% of names are unique. ## Where this shows up in Entity Bind Three pages where this term stops being vocabulary and starts changing an answer, a payload or a price. - [Company registration number (Company number)](https://entitybind.com/identifiers/company-number): One registration in one register. That is not quite the same as one company. - [Register coverage](https://entitybind.com/coverage): The registers the resolver reads, the licence each one publishes under, and how often a live entity's name is unique once it is tidied to a common form. - [Compared with the Companies House API](https://entitybind.com/compare/companies-house-api): The register's own API, its rate limits, and the UK lookups that genuinely need nothing else. The fastest way past a definition is a file: which of your rows are the same company, which of your existing matches we would not have made, and what we could not decide. [Start free →](https://app.entitybind.com/app?signup=1) ## The terms next to this one Each with its own sentence, because the next question is usually about the word beside this one. - [LEI (Legal Entity Identifier)](https://entitybind.com/glossary/lei): The LEI is a 20-character ISO 17442 code identifying a legal entity that participates in financial transactions, issued through the Global LEI Foundation and published as open reference data. - [Crosswalk](https://entitybind.com/glossary/crosswalk): A crosswalk is a mapping between the identifier schemes that name the same company in different systems — LEI to company number to CIK to ticker — so that data joined on one key can be joined to data keyed on another. - [Deterministic matching](https://entitybind.com/glossary/deterministic-matching): Deterministic matching decides a pair by an explicit rule — usually agreement on a strong identifier — and produces the same verdict every time with no score in between. - [Reference data](https://entitybind.com/glossary/reference-data): Reference data is the slow-changing, externally defined data used to classify and identify things — registers, code lists, identifier schemes — as opposed to the transactional data that refers to it. - [SIREN and SIRET](https://entitybind.com/glossary/siren): SIREN is the nine-digit identifier France assigns to a legal unit and SIRET is the fourteen-digit identifier of one of its establishments — the same company at two different levels of granularity. - [Normalisation](https://entitybind.com/glossary/normalisation): Normalisation rewrites a record into a comparable form — case, punctuation, legal forms, identifier shapes — before any comparison is attempted, and it is where most of the achievable accuracy in entity resolution is won or lost. ### Answered at length elsewhere - [United Kingdom](https://entitybind.com/coverage/united-kingdom) (Jurisdiction): Companies House under the Open Government Licence v3.0, storable and resellable. The register every published tier rate on this site was recorded on. ## The other 8 terms on this shelf The keys company data is joined on, who issues each one, and where each stops being unique. - [Crosswalk](https://entitybind.com/glossary/crosswalk) - [LEI (Legal Entity Identifier)](https://entitybind.com/glossary/lei) - [CIK (Central Index Key)](https://entitybind.com/glossary/cik) - [Ticker symbol](https://entitybind.com/glossary/ticker) - [SIREN and SIRET](https://entitybind.com/glossary/siren) - [D-U-N-S number](https://entitybind.com/glossary/duns) - [EUID (European Unique Identifier)](https://entitybind.com/glossary/euid) - [VAT number](https://entitybind.com/glossary/vat-number) Previous, alphabetically: [Cluster metrics](https://entitybind.com/glossary/cluster-metrics) · Next, alphabetically: [Confidence floor](https://entitybind.com/glossary/confidence-floor) ## Evidence basis Internal fixtures only. The historical 2026-08-29 per-tier recording covers 317 GB companies with identifier-rich arrivals seeding the catalogue first; the context tier includes country and registered-town prose. Its legacy replay has no full-prompt-verified calls and cannot certify current calibration. The September 5 CI reports cover 1,176 labelled pairs and 705 records over 250 companies using offline stubs. These are not independent customer holdouts or live production validation; the 99% minimum-input product target remains unmet. Scope is company and organisation identity only — not people, vessels, bank-account ownership, sanctions or emissions. Results may not be used for eligibility decisions about individuals, including employment, credit and tenancy. ## Start with your own company records. Create your workspace, verify your email and run your first company file. The Free plan needs no card. Create API keys in your workspace when you need an integration. [Start free](https://app.entitybind.com/app?signup=1) · [All 64 terms](https://entitybind.com/glossary) 300 credits. No card. For a guided review of your file, explore [the Merge Safety Sprint](https://entitybind.com/audit-pack). --- Entity Bind resolves companies and organisations only. It does not resolve people, vessels, bank-account ownership, sanctions exposure, emissions or geolocation, and its results may not be used for eligibility decisions about individuals, including employment, credit and tenancy. This is the Markdown copy of https://entitybind.com/glossary/company-number, assembled from the same data the page renders and carrying every sentence, table row, figure and question the page's main content carries. The HTML page is canonical; it adds the layout, the navigation and the interactive parts (the ask panel, the forms), which a copy can name but not run. Every page on the site, with a line on each: https://entitybind.com/llms.txt.