The payer on a patient's invoice will default to the person who is paying for that patient's membership. However, if you have a one-off invoice that should be paid by someone other then the payer of the membership, please follow these directions:
Go to the patient's 'Invoice Tab'
Either click '+ New invoice' or click into invoice you want to change the payer for
In the upper left-hand corner, it will say the payer's name
Clicking that will turn the name into a search box
Search for and select the new payer's name
The invoice will be moved over to the new payer's invoice tab and you will be able to use the payment source on their account to pay the invoice
You can change the payer of the invoice in draft mode or when it has already been issued.