Invoices have many computed properties that can change before settling (such as status). Please use the List all modified invoices endpoint to ensure your records are kept up-to-date.
The value of "status" can be in one of the following four states:
The invoice has not been paid, or payment is still processing.
The invoice has been fully paid.
The invoice is not fully paid and past its due date.
The invoice has been voided and is not due for payment, nor has been paid previously.