A facility's ID is its SIRET (French business registration number).
SIRET numbers are issued by INSEE (the French National Institute for Statistics and Economic Studies). It comprises 14 numerical characters of which the first 9 are the company's SIREN (French government reference number).
This piece of information, the facility's name and its type are the three mandatory items of information for creating a facility.
If a company has multiple facilities, only one may be registered as its primary facility, and only one may be registered as its head office.