The Finalize event stage on the Sales Invoice will lock the invoice and prevent any subsequent edits including the connected Sales Order(s) and Deliveries in the workflow.  However, there is a security setting that can be added to allow certain users to have access to edit Finalized events.

 

For example, when Sales Invoice #51 is Finalized then linked Delivery #47 and Sales Order #55 are also Finalized.  Delivery #48 can be Finalized from the Invoice when generated for the Delivery.