Purchase order on desk with person holding pen

What Is a Purchase Order & How Does It Work?

As a small business owner, tracking your inventory and ordering supplies and sellable goods may not be your favorite task, but it’s certainly essential for the success of your company. Purchase orders are crucial for a well-managed purchasing process, though many businessmen and women don’t understand what they actually are or how to use them for financial success.

In this article, we’ll cover:

  • What a purchase order is

  • What you need to include in a purchase order

  • The difference between a purchase order and an invoice

What is a Purchase Order

A purchase order (PO) is a legally binding document created by a buyer and presented to a seller. Much like your “cart” on an e-commerce site, a purchase order is essentially a list of what you want to buy. It lays out the order details, including quantity and types of products the buyer needs, as well as payment terms and delivery details.

The difference between a purchase requisition and a purchase order is that the latter acts as a contract between the buyer and the seller. By submitting an order, the buyer is committing to purchasing goods or services for the agreed upon amount. Because the order is filled before the buyer receives their bill, a purchase order gives the seller insurance against non-payment.

How Does a Purchase Order Work?

Purchase orders are usually used by small businesses who are ordering goods in large quantities. For example, a pet shop may need to buy several types of dog food from a supplier, and order many bags of each type of food. Here’s the purchase order process the pet shop owner would use to get the goods they need:

  1. The shop owner creates a purchase order laying out exactly what they need from the supplier.

  2. If the supplier has the inventory to fill the order, they’ll accept the purchase order, fulfill it, and deliver the items on the agreed due date.

  3. The supplier will then send a bill or sales invoice for the purchased items.

  4. The buyer pays for the item, and the sale is processed through the seller’s POS system.

Buyers can also create special orders for especially large shipments or recurring purchases. A standing purchase order allows a buyer to purchase the same products many times over using the same PO number.

A blanket purchase order is an agreement between both parties for multiple deliveries over a set period, for a set price. Blanket orders are typically used between companies with a strong relationship and sometimes come with discounts or other incentives.

The Difference Between a Purchase Order and an Invoice

Because purchase orders and invoices are both legally binding documents that are exchanged between sellers and buyers, it’s not surprising that they’re often mixed up. The two are also connected because a purchase order is often used to create an invoice, as a reference for the goods purchased and their prices. However, each document is used at a different point in the buying process and often used by different people, as well.

Here are a few differences between purchase orders and invoices:

Purchase Order

  • Created by the buyer

  • Created before purchase

  • Lays out goods needed

  • Includes proposed payment details


  • Created by the seller

  • Created after purchase

  • Confirms goods delivered

  • Requires payment on a specific date

When to Use a Purchase Order vs. an Invoice

A purchase order is used by a buyer to place an order and is issued before delivery.

An invoice is issued by a seller using invoicing software after an order is delivered. It defines the amount the buyer owes for the purchased goods and the date by which the buyer needs to pay.

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How to Create a Purchase Order

Business owners can find online software to help create purchase orders but you can also use a simple Word or Excel document to make your own order forms instead. 

Here’s what you’ll need to include:

  1. Issue date

  2. Products needed and the quantity of each product

  3. Product details including SKU numbers, model numbers and brand names

  4. Price of each product per unit

  5. Delivery date

  6. PO number

  7. Business information including the shipping and billing address, company name and contact information

  8. Terms for payment, such as “paid upon delivery” or specific payment date options

What Does a Purchase Order Look Like?

Purchase orders also look very similar to invoices–at the top, you have the contact information and details for each company, plus the PO number and date. Below that information is generally a table with the products, quantities, details and prices in separate columns. At the bottom of the purchase order, you’ll place the total order amount, the total price and any other order or payment terms along with an authorized signature.

Benefits of Using Purchase Orders

For the buyer, purchase orders are useful for tracking inventory and purchase history. Plus, the buyer can order goods in advance without having to pay right away. Similarly for the seller, purchase orders help track inventory, recurring orders, and more. Best of all, this documentation commits the buyer to paying once the order is fulfilled, giving the seller peace of mind and legal security. 

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Lindsey McGee