Billing notifications

Regardless of whether your tenant shows invoices to view (meaning that you purchase some services directly from Microsoft) or not, you'll have a list on this page of everyone that's authorized to receive billing statements. Whether the billing statements will be directly attached to the emails or not is a switch you can toggle On and Off:

Billing notifications page

You cannot directly add to this list; it's a list of all global and billing administrators, and any custom administrator that contains billing administration rights. However, by clicking on a user in this list, you can change what administration rights they have, which can effectively delete them from the list if you downgrade their rights.