Metered billing
Metered billing is a pricing model where a client is charged based on their consumption level of the product or service.
There are three ways to implement metered billing:
You can configure and set up a Metered Billing product with different pricing models and add it to the subscription as described here and here
You can use additional costs.
Under Customers > Customers open the Customer Details page by double clicking on the concerned customer in the list.
In the Subscriptions box, click on the subscription you would like to change.
In the Pending costs and credits box, click on Add costs.
Enter the Description, Quantity, Price and VAT rate to the Order line.
Click on Confirm.
You can generate an on-demand invoice for the subscription.
Under Customers > Customers open the Customer Details page by double clicking on the concerned customer in the list.
In the Subscriptions box, click on the subscription you would like to change.
In the Invoices box, click on Create invoice.
In the Invoice options include Additional order lines.
Configure the rest of the invoice options.
Click on Submit.