A SIRET number is a 14-digit identifier used in France to pinpoint the precise location of a business establishment. It's a combination of the 9-digit SIREN number (which identifies the company) and a 5-digit NIC (Numéro Interne de Classement) that specifies the individual establishment. A company can have multiple SIRET numbers (one for its head office and one for each of its branches), but only one SIREN number.