Dues Billing
The dues billing module has a way to create member credits, and those credits can be used to make payments on invoices.
Updated 6 days ago
Go to the Dues Billing screen then click the gear icon and choose the "View Member Credit" option
You will see a list of members. Click on the one for which you want to create the credit
You will see the credits that have been created for the member
To add a new one click the add button in the lower right
When a new invoice is created it will automatically be applied to it
The credit can be used to make a payment on an existing invoice