Finalizes a draft invoice, moving its status to open. This is how you advance an invoice for collection: Fintoc never finalizes invoices automatically. When the invoice has a default_payment_method and its collection_method is charge_automatically, Fintoc charges the invoice right after finalizing. Finalizing an invoice that is already open, or a zero-amount invoice that Fintoc already marked as paid, returns the invoice unchanged. You cannot finalize a paid invoice with a positive total or a void invoice.