Answer:
Inquiry Letter
Sometimes a business can send this to a supplier to find out if they have a certain good in stock.
Purchase Requisition
This is a document used by a department in a company to request that those in charge of procurement acquire some goods for them.
Quotation
This is a document sent by a supplier to the prospective buyer informing them of the goods they have and their selling price.
Purchase Order
This is the document that shows a formal request for goods from a supplier.
Delivery Note
This is used to confirm that the buyer has received the goods they ordered. The buyer will typically sign this document to confirm receipt.
Invoice
A supplier prepares and sends this to the buyer to show them the goods they ordered and the prices so that the buyer knows how much they owe.