Company numbers and registers: how they compare

What a company number does

A company number ties a record to one registered entity, even when its name changes. UK law makes the point directly. Section 1066 of the Companies Act 2006 says the registrar must give every company a registered number and decides its form, which may be one or more sequences of figures or letters ¹. If the registrar adopts a new form and changes a number, the old or new number can be used for disclosure for three years ¹.

Tax numbers are a different thing. They are issued by revenue bodies for tax purposes. Brazil's federal revenue service, Receita Federal, says new registrations will get an alphanumeric CNPJ from July 2026, and that anyone already registered keeps a valid number ¹⁰.

Registers side by side

Cross-border search in the EU

The European e-Justice Portal says the business registers of all EU countries have been interconnected and become searchable as of June 2017 ⁸. This gives one entry point to national records ⁸.

Checking a number before you rely on it

• Search the register that issued the number, not a copy. For an ABN, ABN Lookup accepts the ABN, the ACN or the name ³.
• Check the number against its built-in check where one exists. The ABN uses a modulus 89 check on its two leading digits ³.
• Read the previous names field. Companies House shows previous company names for free ².
• Note what costs money. Delaware says additional information beyond the basic details can be obtained for a fee ⁵.
• Write down the date you checked, since registers update.

Where national registers stop

Company registers show who runs a company. Ownership often sits on a separate beneficial ownership register with its own access rules. In the US, the Delaware Division of Corporations is one example of a state register ⁵. Kenya's Companies Registry administers the Companies Act, 2015 and keeps statutory records for companies, limited liability partnerships and business names ⁹.