The invoice settings contains four parts, Invoice frequency/Billing period, invoice date, generate date and due date.
You find the invoice settings from the settings cog top right and then select invoicing.
Invoice Frequency/Billing Period
This determines the frequency of when parents will be invoiced. Multiple option can be offered to parents. These settings only apply for bookings during Term programmes, Holiday and Special day programme bookings are set to have once invoice only for bookings.