When a record is collected for products or services provisioned, these records each contain a few attributes of which Client ID is one. This Client ID is linked to one or more contracts. The contract belongs to a client and a product master. Therefore, whenever a billing record is validated, Varibill will determine for which product the record is collected, and determine the product master to which the product is linked. Once Varibill can establish this, it will determine if there is an active contract for this client and product master combination. Based on this information that specific client is always billed for the record.
Read more on docs.varibill.com for more information on client identifiers.