The Billing Review screen in BillQuick analyzes all recurring projects on their scheduled billing frequency. For projects with contract types other than Recurring, the Billing Review screen analyzes only those projects that have some time or expense entries logged within the chosen billing period. If you would like to bill a client even though you had no activity on account, you can do so by using the Add button in the Billing Review screen or using the Manual Invoice screen.
In BillQuick there is a rule in the Project screen "Always Show in Billing Review". If this rule is turned on, the project will appear in that screen even though you may not have worked on it for the specified billing period. See the BillQuick Help for more details.