Configuring Invoice Settings
WHMCS has the built-in capability to invoice your customers precisely when you want.
You can configure this at Configuration > System Settings > Automation Settings (Setup > Automation Settings in WHMCS 7.10 and earlier).
We also recommend watching our Getting Started with WHMCS: Automation Settings video tutorial.
Choosing When to Run Invoicing
By default, WHMCS runs invoicing and other automated tasks at 9AM local server time.
You can customize this using Time of Day in the Scheduling section.
Specifying Invoice Generation Intervals
By default, WHMCS will generate invoices 14 days prior to the Next Due Date.
You can customize this using the settings in the Billing Settings section:
Specify an Invoice Interval for All Billing Cycles
To invoice all products and domains with any billing cycle (for example, Monthly or Quarterly) with the same interval, modify Invoice Generation.
Specify an Invoice Interval Per Billing Cycle
To specify a different number of days in advance to generate an invoice, one based on the billing cycle (for example, Monthly) and another for domain names, click Advanced Settings next to Invoice Generation.
Use the additional fields that display to set the number of days before the Next Due Date to generate an invoice.
Specifying Invoice Reminder Intervals
After the system sends the invoice to the customer, you may also need to send a reminder to ensure payment. You can configure WHMCS to send a reminder email before the invoice is due as well as several reminders after the invoice is past due.
You can customize this using the Reminder settings in the Billing Settings section: