Scope
Difference between recurring invoice and one-time invoice

The difference between the Recurring Invoices and One-Time Invoices notifications is determined by whether or not the charge has a billing frequency.  For example, a subscription that renews monthly would be considered a recurring invoice as a new invoice is generated each month.  This would be considered recurring and would receive notifications configured under the Recurring Invoices section.

Another example would be charging a customer a one-time charge related to something outside of the subscription price that will not be charged on a frequency basis like monthly or yearly moving forward.  This would be considered non-recurring and would receive notifications under the One-Time Invoices section.