A normal invoice is an invoice which will created after one delivery has been executed. The functionality is started with Create customer invoice.

A collective invoice is not created after one single business case but only in time intervals, e.g. once a week for all business transaction during this interval which will be collected. The functionality is Create collective customer invoice.
 

The settings in the customer data control which kind of invoices are applicable to that customer: either only normal or only collective or both. In the case of both are applicable, the decision is with the user which of the two commands will be used.

When we use combined “Normal and Collective” invoice type as the customer invoice type, it allows you to generate invoices that include both individual customer orders and summary invoices for multiple orders. This type is useful when you need flexibility in your invoicing process, accommodating both single order invoices and collective invoices.

As an example I have selected this for one of my customer, so if I want to create separate individual invoices for that customer on specific orders those orders can be filtered in the Create Customer invoices window. But if I want to create collective invoices for the customer, if you search in the Create Collective Customer Invoices window in there also you can view the available orders to be invoiced as a collection.

Hope this helps point you in the right direction. :-)

Thank you for your help!

That was straightforward. So, we can update the invoice type for all customers who have "collective" to "normal and collective" to enable the use of staged billing, while also ensuring that the jobs that create invoices for these customers generate collective invoices when desired.