A purchase order (PO) is an official document that a designer sends to a supplier to indicate the types, quantity, and price of the products or services being sold. Purchase orders are commonly used when purchasing products on account and are needed by suppliers to fulfil orders and process payments. Essentially, a purchase order defines the contract of the sale and is created before an invoice is sent.

Purchase orders provide legal and enforceable records of exactly what you ordered and guard against unexpected price increases. If you receive the wrong quantity or type of items or are charged the wrong amount, you can refer to the purchase order to resolve the issue.