WHAT IS THE DIFFERENCE BETWEEN PERFORMA INVOICE & INVOICE RAISED AFTER SALES DELIVERIES OR MATERIALS RECEIVED INVOICE? Give with examples.

Proforma Invoice is a draft invoice with an estimated value of goods that can still be edited or recomputed. This is usually used for documentation purposes only like customs clearance and or pre-invoice documentation for delivery . While Sales Invoice after delivery are final invoices with final value or amount to be billed to the buyer.