Purchase Order vs Bill: A Simple Guide

The One-Sentence Summary

A purchase order is what you send to a supplier to request goods or services. A bill (also called a vendor invoice) is what the supplier sends back to you requesting payment.

They're two sides of the same transaction — but they serve different purposes and are created at different points in the procurement workflow.

What Is a Purchase Order?

A purchase order (PO) is a formal document from a buyer to a seller that authorises a specific purchase. It's sent before the goods or services are delivered.

A standard purchase order includes:

A unique PO number (for tracking)

Your business name and billing address

The supplier's name and address

An itemised list of goods or services requested

Quantities and agreed unit prices

Delivery address and requested delivery date

Your authorised signature or approval

Once the supplier accepts the purchase order, it becomes a binding agreement. They'll deliver the goods or perform the service as specified.

Why Use Purchase Orders?

Many small businesses skip purchase orders entirely — especially for small or regular purchases. But POs provide real benefits:

Budget control. Every purchase is pre-authorised. Nobody on your team can spend money without a PO being raised and approved.

Dispute protection. If a supplier delivers the wrong goods or charges more than agreed, the PO is your reference point. "We ordered 50 units at $12 each, per PO-2025-047" is a much stronger position than "we discussed it over email."

Audit trail. Accountants and investors love purchase orders because they create a clean paper trail from commitment to delivery to payment.

Inventory accuracy. Knowing what you've ordered (but not yet received) helps you manage stock levels without over-ordering.

What Is a Bill?

A bill — or vendor invoice — is the document the supplier sends to you after delivery, requesting payment. It's essentially an invoice, but from the vendor's perspective rather than yours.

A bill should contain:

The supplier's business name and contact details

Your business name and billing address

A reference to the purchase order (if applicable)

An itemised list of goods or services delivered

Unit prices and totals

Payment due date and accepted payment methods

When you receive a bill, your job is to verify it against the original purchase order and delivery note: were the right items delivered? Is the price correct? Are the quantities accurate?

This three-way matching process (PO + delivery note + bill) is standard practice in businesses with any purchasing volume.

The Procurement Workflow

Here's how a typical purchasing transaction flows:

Raise a purchase order — you send PO to supplier

Supplier confirms and delivers — goods arrive with a delivery note

You receive the goods — verify against PO and delivery note

Supplier sends bill — their invoice for the delivered goods

You pay the bill — on or before the due date

Record keeping — PO, delivery note, and bill are all stored together

Quotation Expert handles steps 1, 2 (delivery note), and 4-6 in one connected workflow. Raise a PO, convert it to a delivery note when goods arrive, and convert it to a bill when the vendor invoice comes in. Everything is linked — no duplicate data entry.

Key Differences at a Glance

Purchase Order:

Created by: the buyer (you)

Timing: before delivery

Purpose: authorise a purchase

Creates obligation on: the supplier (to deliver)

Bill:

Created by: the supplier

Timing: after delivery

Purpose: request payment

Creates obligation on: the buyer (you) to pay

When Small Businesses Can Skip Purchase Orders

For many very small businesses — a sole trader buying from a handful of regular suppliers — formal POs may be unnecessary overhead. If you're buying the same supplies from the same two vendors every month and the amounts are predictable, a more informal approval process may make sense.

As a general rule, consider implementing formal purchase orders when:

Your team has more than one person with purchasing authority

Your monthly purchasing exceeds a threshold you'd want to track (e.g., $1,000+)

You have inventory and need to track incoming stock

You're dealing with new or unfamiliar suppliers

The cost of a disputed or wrong delivery almost always exceeds the time spent raising a proper PO.