What is the main difference between a purchase order and an invoice?

A purchase order (PO) is issued by a buyer to a vendor BEFORE goods or services are delivered — it authorizes the purchase and establishes terms. An invoice is issued by the vendor AFTER delivery to request payment. In short: PO = authorization to buy; Invoice = request to pay.

When should I use a purchase order vs an invoice?

Use a purchase order when you are buying goods or services as a business and want to formalize the order before delivery — especially for large orders, B2B purchases, or when you need budget approval. Use an invoice when you are requesting payment after goods or services have been delivered. If you're a freelancer or vendor billing a client, you issue an invoice — not a PO.

Does a purchase order mean I have to pay?

Yes — a PO is a binding commitment to purchase. Once a vendor accepts your PO, you've agreed to pay for the goods or services listed. An invoice, by contrast, is a request for payment that hasn't necessarily been pre-authorized in the same way. Always review an invoice against its corresponding PO before paying.

Can I create a purchase order and invoice with the same tool?

Yes. Eonebill lets you create both purchase orders and invoices from the same platform — and with AI, you can generate either document in 15 seconds flat. Describe what you need in plain English and Eonebill builds the correct document type automatically.

Which document comes first — purchase order or invoice?

The purchase order always comes first. The buyer creates a PO → the vendor acknowledges/accepts it → goods or services are delivered → the vendor sends an invoice. Skipping the PO step and going straight to invoicing is common for small purchases or one-off freelance work, but formal B2B procurement always starts with a PO.

Product Hunt

If you've ever wondered whether you need a purchase order or an invoice for a particular transaction — you're not alone. These two documents look similar on the surface. Both list items, quantities, and prices. Both travel between buyers and vendors.

But they serve opposite ends of a transaction. Getting them wrong means budget overruns, payment disputes, or orders that never get authorized.

This guide breaks down purchase order vs invoice — every meaningful difference, when to use each, and how Eonebill AI handles both so you never create the wrong document again.

What Is a Purchase Order (PO)?

A purchase order is a commercial document issued by a buyer to a vendor, authorizing the purchase of goods or services under specified terms. It is not a request for payment — it is a commitment to buy.

A PO typically includes:

Vendor name and address
Buyer name and address
PO number (for tracking)
Line items with quantities and agreed prices
Payment terms
Delivery date and location
Any special terms or conditions

Think of a PO as the buyer's purchase authorization: "Yes, I want to buy these items from you, here's the agreed price, please proceed."

When a PO Is Issued

A purchase order is created before goods or services are delivered. The buyer initiates it to:

Formally authorize the vendor to begin fulfilling an order
Lock in agreed pricing and quantities
Establish terms (delivery date, payment terms, return policy)
Provide their accounting team a record of a pending obligation

In many businesses, a PO is required before any vendor can ship goods or start work. The PO is essentially a budget pre-approval document.

A Real-World PO Example

A restaurant owner orders $3,000 worth of food supplies from a distributor. Before the truck arrives, the restaurant's purchasing manager creates a PO:

> PO #1042

> Buyer: Riverside Restaurant, 45 Main St, Chicago

> Vendor: Midwest Food Supply Co.

> Items: Produce order — 50 lbs tomatoes, 30 lbs onions, 20 lbs peppers — $3,000 total

> Delivery: April 10, 2026

> Terms: Net 30

The distributor receives the PO, confirms availability, and ships the goods. After delivery, the distributor will issue an invoice matching the PO.

What Is an Invoice?

An invoice is a commercial document issued by a vendor to a buyer, requesting payment for goods or services that have been delivered. Unlike a PO, an invoice comes after the work is done.

An invoice typically includes:

Vendor name, address, and contact info
Buyer name and billing address
Invoice number and issue date
Line items with descriptions, quantities, rates
Subtotal, taxes, discounts, and total amount due
Payment terms and accepted methods
Due date

An invoice is a payment demand backed by a delivered obligation. The buyer has received value; now they need to pay for it.

When an Invoice Is Issued

An invoice is created after goods or services are delivered. The vendor issues it to:

Formally request payment from the buyer
Provide a legal record of the transaction for both parties
Trigger the buyer's accounts payable process
Enable the buyer to match the invoice against their PO for verification

A Real-World Invoice Example

The restaurant receives the produce order from Midwest Food Supply Co. The distributor then issues an invoice:

> Invoice #INV-8831

> Vendor: Midwest Food Supply Co., 800 Industrial Blvd, Milwaukee

> Buyer: Riverside Restaurant, 45 Main St, Chicago

> Items: Produce order per PO #1042 — $3,000

> Tax (6%): $180

> Total Due: $3,180

> Due: May 10, 2026 (Net 30)

The restaurant's accounts payable team matches the invoice to PO #1042, verifies the delivery, and processes the payment.

Side-by-Side: Purchase Order vs Invoice

| Dimension | Purchase Order (PO) | Invoice |

|---|---|---|

| Who Issues It | Buyer | Vendor |

| When It's Issued | Before delivery | After delivery |

| Purpose | Authorize purchase | Request payment |

| Legal Effect | Buyer commits to buy | Vendor demands payment |

| Accounts Impact | Creates a "pending purchase" liability | Triggers accounts payable |

| Payment | Not requested — it's the promise to pay | Explicitly requests payment |

| Matching | Vendor matches against their sales order | Buyer matches against their PO |

| Reversal Risk | Can be cancelled before fulfillment | Can be disputed after delivery |

| Common For | B2B procurement, large orders, inventory | Freelance billing, service delivery, final payment |

The Purchase Order Process (Step by Step)

Understanding the PO-to-payment workflow is essential for both buyers and vendors.

For the Buyer:

Identify a need — Your team needs materials, supplies, or services
Select a vendor — And confirm they can fulfill the order
Create a PO — Using your procurement system (or Eonebill), list items, quantities, agreed prices, and terms
Submit the PO to the vendor — The vendor reviews and accepts (or negotiates changes)
Receive goods/services — Verify delivery matches the PO
Match the invoice — When the vendor invoices, match it to your PO to verify accuracy
Process payment — Pay the vendor per agreed terms

For the Vendor:

Receive the PO — Review items, quantities, and pricing
Accept or negotiate — Confirm you can fulfill the order at the listed terms
Fulfill the order — Ship goods or deliver services
Issue an invoice — After delivery, invoice the buyer referencing the PO number
Receive payment — Per the payment terms on the invoice

The Invoice Process (Step by Step)

For the Vendor (Sender):

Complete the work — Deliver goods or finish services
Prepare the invoice — List all deliverables, amounts, taxes, and totals
Add payment terms — Due date, accepted methods, late fee policy
Send the invoice — Email directly or through a platform like Eonebill
Follow up if needed — Send reminders for overdue invoices
Record the payment — Mark the invoice as paid when received

For the Buyer (Recipient):

Receive the invoice — Cross-reference it with your PO
Verify goods/services were received — Confirm the delivery matches the invoice
Approve for payment — Route to accounts payable
Pay by the due date — Via ACH, credit card, or your payment system
Match and close — Mark the invoice as paid in your records

Common Scenarios: When to Use a PO vs an Invoice

Freelancer Sending a Client Bill

→ Use an Invoice. You're the vendor, you've completed the work, and you need payment. Issue an invoice.

Large B2B Order for Office Furniture

→ Use a PO first, then an Invoice. The buyer issues a PO to authorize the $12,000 furniture order. The vendor accepts, ships the furniture, then issues an invoice for $12,000.

Contractor Billing for Completed Design Work

→ Use an Invoice. The design is done. Send the client an invoice for the work completed.

Manufacturing Company Ordering Raw Materials

→ Use a PO. The manufacturer creates a PO for 500 units of component X at $8/unit. The component supplier accepts and ships. After delivery, they invoice for 500 × $8 = $4,000.