The charge service runs automatically every hour. It generates invoices for any charges (recurring invoices) that commence or are scheduled to run during the current charge period.
The charge period is calculated by taking the current date and adding the number of days that were defined in your configured billing rules. See: Merchant Tab/Billing Rules/Invoicing/# Days in advance to generate invoices field.
The charge service was designed to make it easy to submit a debit order batch for collection before the date it has to be collected.
Note: If you need to urgently process a batch of invoices for payment, you can manually trigger the charge service to initiate the immediate generation of invoices. Do this by clicking the Process Recurring Invoices button located on the Recurring Invoices Management.