You may come across the following message if this scenario comes up:
In the case of invoicing a contact for a single matter, the payment recorded would NEED to be generated and linked to both, the Contact AND Matter.
If you are generating an invoice that will include Several matters(2+ matters) on the bill, then the payment would NEED to be generated ONLY to the contact.
Note: If the Matter dropdown menu AUTOMATICALLY selects a matter, you can unselect it by clicking on the 'x' to the left of the dropdown menu.