The official business definition of Quote, Purchase Order, and Invoice is a three-step process used to complete a transaction. A Quote is a document that is sent to a customer to provide an estimate of the cost of goods or services. A Purchase Order is a document that is sent from a buyer to a seller, specifying the goods or services that the buyer wishes to purchase. An Invoice is a document that is sent from a seller to a buyer, detailing the goods or services that were purchased and the total amount due. This three-step process is used to ensure that both parties understand the terms of the transaction and that the goods or services are delivered as expected. The Quote, Purchase Order, and Invoice are all important documents that are used to track and record transactions, and they are necessary for any business to operate efficiently.