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Purchase Order vs Invoice: Key Differences Explained

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A purchase order is a document sent by the buyer to the seller to place an order for supplies or services, while an invoice is sent by the seller to the buyer to collect payments for the purchased goods.

Have you ever wondered how successful businesses track their purchases? Or how do they manage inventory seamlessly? The key is a document called a purchase order.

Whether you're an experienced business owner or just starting out, understanding the role of purchase orders is crucial for efficient and effective business management.

In this article, we will explain what a purchase order is, why it’s important, and how it’s different from an invoice. We will walk you through how this document makes the procurement process smoother and more organized for businesses of all sizes.

What Is a Purchase Order?

A purchase order (PO) is a document that a buyer sends to the seller to request a purchase. It outlines order details, product specifications, quantity, billing terms, and shipping terms.

Typically, placing a purchase order initiates the sales transaction, and the order becomes a legally binding document once the seller accepts it. This means that the customer is obligated to pay for the purchase, and the seller is committed to delivering the goods or services. 

Because of this status, a purchase order offers legal protection for the supplier against non-payment or order cancellation. 

Additionally, a blanket purchase order is commonly used by customers who want to arrange a recurring delivery of the same supplies at the same price for an extended period. 

A purchase order is an essential document for a purchasing department to keep records of the company purchases and spending and for an accounts payable department to match the order with future invoices. 

💡Tip: A purchase order only becomes a legally binding contract after the supplier accepts the request. Sometimes, the seller may reject a purchase order request due to product availability or quality standards. 

What Details Does a Purchase Order Include?

A purchase order typically includes 

  • Purchase order number: A unique identifier for easy reference and tracking.
  • Date of issue: The date when the purchase order is placed.
  • Buyer’s information: The name, address, and contact details of the buying company or individual.
  • Seller’s information: The supplier's name, address, and contact details.
  • Billing address: The address where the buyer receives and processes invoices.
  • Shipping address: The address where the order will be delivered.
  • Order information: Descriptions of the products or services being ordered, including quantity, unit price, and other relevant details
  • Total price: The total cost of the order.
  • Payment terms: Details about the payment, including payment methods and due date.

⚠️ Caution: Always ensure that the details are correct before sending a purchase requisition to avoid unnecessary disputes.

Example of a Purchase Order

There is no universal way to format a basic purchase order, but the details should be laid out clearly. Here is an example of a professional-looking purchase order.

an example of a payment order

When to Use a Purchase Order

Typically, businesses issue a purchase order to order supplies or services from a supplier. Here are examples of situations when you or the procurement team may have to prepare this document.

  • You are a buyer initiating the buying process and want to confirm that the seller can provide the supplies or fulfill your terms of purchase.
  • You want to specify details such as the quantity of goods or services, specific quality, price, expected delivery date, payment terms, etc.
  • You are ordering a large quantity and want to have a written record of your order to avoid misunderstandings or disputes with the supplier.
  • You want to track your pending spending and inventory and manage your cash flow.

What Is an Invoice?

What Is an Invoice?

An invoice, or sales invoice, is an official document that a seller issues to collect payments for goods or services rendered. Invoices are important in sales transactions and are crucial in financial reporting, taxation, budgeting, and accounting, as they provide tangible evidence of outgoing expenses and incoming payments.

After the seller completes the terms of purchase, they will issue an invoice to collect payment from the buyer. An invoice also serves as a legal document that binds the buyer to pay the seller for the purchase. 

💡Tip: An invoice is different from a bill, which is more commonly used in one-time B2C sales transactions.

What Details Does an Invoice Include?

Depending on the purposes, businesses in different industries may use different types of invoices. However, these are the essential details that must be included on every invoice:

  • Invoice number: A unique invoice number used to identify, track, and record transactions.
  • Date of issue: The date when the invoice is issued.
  • Purchase date: The order date.
  • Seller’s information: The supplier's name, address, and contact details.
  • Buyer’s information: The name, address, and contact details of the buying company or individual.
  • Purchase details: An itemized list of the purchased goods or services, including product details, quantity, and price per unit.
  • Applicable discounts or taxes: Any discounts or sales taxes should be calculated before concluding the total price.
  • Total price: The total amount that the customer has to pay.
  • Payment terms: Details about the payment, including payment methods, due date, and late payment fees.

💡Fact: 39% of invoices are paid late in the United States. To get paid on time, make sure to include all the essential details clearly when creating an invoice.

Example of an Invoice

Here’s what a basic invoice looks like. There are also no regulations about how to format an invoice, but every essential detail should be provided with clarity and transparency. 

An example of an invoice

💡 Tip: After receiving invoice payments from the customers, the seller should always issue uu7 se a receipt as proof of payment.

When to Use an Invoice

Normally, a standard invoice is sent when the seller is requesting payment from the buyer. Let’s look at the examples of when you would need to issue an invoice.

  • You have delivered goods or services to a customer and want to collect payment.
  • You want to provide a detailed breakdown of your goods or services, such as description, quantity, price, taxes, discounts, etc.
  • When the client requests a preliminary invoice to confirm the order and the estimated cost, you can issue a pro forma invoice.
  • You may have to issue a commercial invoice if you are shipping the products internationally. 
A graphic of Statrys' Invoice Management tool.

Differences Between a Purchase Order and an Invoice

Purchase orders and invoices are two essential documents in the procurement process. Although they share similar details, the key difference between a purchase order and an invoice is when it is issued and for whom.

  • Purchase Order: Issued by the buyer to place an order; sent before receiving the product or service.
  • Invoice: Issued by the seller to request payment; sent after product delivery or service completion.

Apart from these, there are also other factors that make a purchase order different from an invoice. 

Let's take a closer look at them.

  Purchase Order Invoice
Purposes Request confirmation to supply goods Request payment for goods or services provided
Usage Simplify inventory management Facilitate accounting and financial management processes
Sender Buyer Seller
Content Provide terms of purchase, including billing and shipping details Provide payment terms, including final price, payment methods, and payment due date
Timing When placing the order When the order is fulfilled
Payment Do not require payment Require payment

Having both purchase orders and invoices is all about clear communication. The purchase order sets the stage, and the invoice wraps up the show. It’s a clear two-step that keeps everything transparent and agreed upon.

Sudhir Khatwani
Sudhir Khatwani
Director & CEO, The Money Mongers


How important is a purchase order to your business?


For us, purchase orders are key. They're our roadmap for upcoming projects and purchases, laying out what we need and expect. This clarity is a big help in budgeting and keeping our financial ducks in a row.

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Are purchase orders still relevant in the digital age?


Are you using software to manage your invoices? Would you recommend automating the process?



In essence, a purchase order is a formal request made by the client to the seller to purchase goods or services, outlining the client's expectations and terms for the transaction. Once the seller accepts the purchase order, it becomes a legally binding agreement, obligating them to deliver the specified goods or services.

On the other hand, an invoice is an official request for invoice payment issued by the supplier to the client when the order is completed per the terms established in the purchase orders.


Apart from its primary function, the buyer can conveniently track the progress and status of the order by referring to the purchase orders. This type of document also assists in maintaining an accurate inventory record and thus prevents overstocking.

At the same time, invoices can be used to simplify the accounting and payment processes. Keeping an organized invoicing management facilitates the team to calculate company spending and taxes, as well as reduce the risks of duplicate payments.


A customer sends a purchase order, whereas the vendor sends an invoice. 

In businesses, the sender of purchase orders is usually the purchasing department, while the sender of invoices is usually the billing department.


Although both purchase orders and invoices contain similar pieces of information, such as the contact information of both the buyer and the seller and product or service details and quantity, there is information specific to each document.

Purchase orders typically include the buyer’s billing and shipping address, purchase order number (PO number), and delivery terms. They contain information the seller needs to know to process and deliver the order.

Invoices, on the other hand, contain invoice numbers and details about the payment, especially payment methods, due dates, and payment terms. Invoices would provide the details necessary for the buyer to pay for the purchase. 


Purchase orders are issued before the delivery of goods, while invoices are sent at the same time or after the shipment. A purchase order is typically sent before an invoice in a buying process.

Let’s briefly look at the timeline of when each document is issued during the purchase order process.

Sales quote Purchase order → Order confirmation Invoice Receipt

Similarities Between a Purchase Order and an Invoice

Despite the differences between a purchase order and an invoice, they share some similarities:

  • Both documents are crucial in the purchasing process.
  • Both documents are means of communication between the buyer and the seller, and both provide transparency in the transaction.
  • Both a purchase order and an invoice provide product or service details, including quantity and price. 
  • Both documents follow a similar format and layout, usually with headings, tables, and totals.
  • Both are legally binding documents and can be used for auditing, accounting, tax, inventory control, and budgeting purposes. 

Why Do Businesses Need Both of Them?

Purchase orders and invoices are crucial documents that help businesses of all sizes and across different industries run smooth internal operations. 

While a purchase order ensures efficient inventory management, an invoice contributes to an organized accounting process. Using both purchase orders and invoices effectively can streamline and improve your business’s purchasing, budgeting, and cash flow management.

Additionally, consider going digital instead of manually managing purchase orders and invoices. Studies show that e-invoicing can save up to 70% of the costs compared with paper billing. Using tools like Statrys Invoicing Software is an efficient and convenient way to manage your invoices and simplify a part of your sales and purchase transactions.

a screenshot of Statrys' invoicing software


Is the purchase order and invoice the same thing?

No, they are not. Customers use a purchase order to request and confirm the supply of their order from sellers. On the other hand, an invoice is used by sellers to request payment from their customers. 

What comes first, a purchase order or an invoice?


Can you send an invoice without a purchase order?


Why Is a purchase order important?


What is a PO?

Fact checked by
Djon Ly

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