Billing the Overage of a Consumption-Based Product
A metered resource is considered overaged when the usage of this resource has exceeded the quota the product manager defined for this resource in service definition. A typical example is the bandwidth of a Virtual Machine. If for a Virtual machine offering the bandwidth quota has been set to 2 TBs / month and a VM has consumed 2.3 TBs in a month, then the customer must be billed for the extra 0.3 TBs he consumed. For billing resources overage the following steps must be followed:
Define an Overage Rate for a Service Resource
An add-on must be declared for charging resources overage. Using an add-on you can define the unit of measure (e.g. if the bandwidth overage will be charged per 1 GB or per 10 GBs), the unit price and any volume discount that can be applied to overage charges. An add-on has the same type with the service and is related with a specific service resource.
Define which Service Resources can have Overage
The next step is to define which resources of a service can have overage. This is accomplished through the Pricing section in service's details page. In this section there is the tab Usage Charges where you can define which resources are charged based on usage and which add-ons will be used for billing the resources overage.
Define that resource "Monthly bandwidth per VM (GB)" is a metered resource that is charged based on usage using the add-on "Traffic Overusage (10G)"
An add-on for defining the overage rate for the bandwidth of a Virtual Machine
Import Usage Data for Resources Overage
For billing the resources overage we must first import in Cloud BSS the usage records for these resources. You can import usage records from excel spreadsheets directly into Cloud BSS using our Usage Data importer. The Usage Data Importer is accessible through “Usage Data” menu in “Billing” module. Since usage data are always billed in arrears, the import of the usage data must be performed the last day of the billing cycle (i.e. on July 31st for charging overage for the July month)
For charging usage overage, you must define in excel spreadsheet not the total resource consumption but only the amount is considered overaged. For example, if a virtual machine consumed in total 2.282GBs in a moth and the assigned quota was 2TBs, then in excel the usage record must have as quantity 234 GBs.
a usage data excel for importing bandwidth overage from specific servers
Upon import completion, the imported usage records will be related with the correspondent subscriptions. 
For more information about the Usage Data importer tool, please check the /wiki/spaces/ICPD/pages/801112099 page.
The imported usage record is related with the correspondent subscription
Billing Resources Overage
The imported usage records are billed to the customer when the related services are billed. The charges will be calculated based on the rate plan defined in related add-on. If for example the bandwidth overage was 234 GBs, then the customer will be charged 24 times the add-on "Traffic Overusage (10G)".