The customer payment rule means that when an invoice has not been settled, the revenue calculation always defers the invoice revenue. If the invoice has been settled in full—not partially settled—the invoice revenue is always recognized.

The invoice payment date is also important because you can set an effective date for the revenue calculation. If you run the revenue calculation before the invoice payment date, then even when the invoice is flagged as settled, the revenue from the invoice is still deferred. Otherwise, the revenue of the invoice is recognized.