What is the correct customer contact setup at site level to facilitate the sending of invoices?

Summary:

We have examples of the wrong customer contact receiving copies of invoices. What is the right setup to ensure that the right contact gets the invoice?

Content (please ensure you mask any confidential information):

We had been advised that only customer contacts with a bill-to responsibility would be sent invoices. However, we have examples where the primary contact only has the Acknowledgements responsibility but is receiving the invoices.

Is is the Primary flag that is determining the contact for invoice receipt?

Version (include the version you are using, if applicable):

25D

Code Snippet (add any code snippets that support your topic, if applicable):