Correctly registered French businesses can be identified by their SIRET and SIREN numbers, which are created when the (new) business is established.
Registrations are handled either by the CFE ('centre des formalités des entreprises') at the local chamber of commerce or the 'chambre des métier' for occupations classed as 'artisanal'. There are also special CFEs for some occupations such as commercial agents among others. In the case of the new 'auto-entrepreneur' (self employed) regime, declaration of the start-up of the business can be made using downloadable forms. See the website www.auto-entrepreneur.fr for more information.
Once the registration formalities are completed, the CFE forwards the documents to the tax office, social security etc, and eventually the new business will be issued with an identifying code, known as its SIREN (9 digits) and a SIRET number composed of the SIREN plus a further 5 digits, identifing the place(s) where the business operates. This information can be used to find information about a registered business using the site www.infogreffe.fr - similar to checking the UK Companies House online.
If the business operates under a TVA/VAT regime, it should also be issued with an Inracommunautaire TVA number which is made up of part of the SIREN plus an 'F' country prefix for France.
French business occupations are also classified nationally by code numbers, known as the APE code appropriate to their activity, but this is largely for statistical purposes.