What is a purchase order?

A purchase order, or PO, is a document a buyer sends to a supplier that formally requests goods or services at agreed quantities, prices and terms. Once the supplier accepts it, the PO becomes a binding agreement. It is the buyer's written commitment to buy, created before the goods are delivered, which is what separates it from an invoice.

What is the difference between a PO and an invoice?

A purchase order is raised by the buyer before delivery and states what they want to buy. An invoice is raised by the supplier after delivery and requests payment for what was supplied. The PO records the agreed order, the invoice claims the money, and matching the two ensures you only pay for what you actually ordered and received.

What is a three-way match?

A three-way match is a check that compares three documents before payment: the purchase order (what you ordered), the goods receipt note (what you received), and the supplier invoice (what you are billed for). When quantities and prices agree across all three, the invoice is cleared for payment. If they disagree, the difference is investigated first. It is the main control that stops overpayment and fraud.

Do small businesses really need purchase orders?

Yes, once you buy regularly from suppliers. A PO turns a verbal or WhatsApp order into a written record of agreed price and quantity, which prevents the most common disputes: wrong quantity delivered, a price higher than quoted, or a charge for something you never ordered. Even a simple numbered PO template gives you that protection.

What is a purchase requisition?

A purchase requisition is an internal request to buy something, raised by a team or a person and approved by whoever controls the budget, before any purchase order goes to a supplier. It is the internal go-ahead. The purchase order is the external document that follows once the requisition is approved.

Purchase Order Process: What a PO Is and How to Manage It (2026)

Many small businesses in India buy on trust: a phone call, a WhatsApp message, a verbal price. It works until it does not, and then you are arguing over how many units were ordered, what price was agreed, or why you were billed for something you never asked for. A purchase order fixes this by putting the agreement in writing before the goods move. This guide explains what a PO is, how the full purchase-to-payment flow works, how a PO differs from an invoice, and why a little paperwork up front saves a lot of arguments later.

What a purchase order is

A purchase order, or PO, is a document the buyer sends to a supplier that sets out exactly what is being ordered: the items, the quantities, the agreed unit prices, the delivery date and the payment terms. Each PO carries a unique number so it can be tracked. When the supplier accepts it, the PO becomes a binding commitment on both sides. The key point is timing: a PO is created before the goods are delivered, so it records what was agreed, not what was later claimed.

The procure-to-pay flow

A PO is one step in a larger flow that runs from deciding you need something to paying for it. This flow is often called procure-to-pay, and it has five clear stages.

Requisition: someone inside the business raises an internal request to buy, and whoever controls the budget approves it. This is the internal go-ahead before anything is sent to a supplier.
Purchase order: once approved, a numbered PO is issued to the chosen supplier with the agreed items, quantities, prices and terms.
Goods receipt: when the goods arrive, they are checked against the PO and a goods receipt note is recorded, capturing what was actually received and in what condition.
Invoice: the supplier sends an invoice requesting payment for what was supplied.
Payment: after the documents are matched, the invoice is cleared and paid within the agreed terms.

Each stage feeds the next, and each produces a record. Tie those records together and you always know what was ordered, received and billed, without relying on anyone's memory. Recording goods receipt against the PO also keeps your stock records accurate, because incoming quantities update inventory at the moment they arrive.

Track stock and bill in one place

IndiaCRM includes Inventory and GST billing: stock, purchase orders and invoices that stay in sync, free. Create your free account.

The three-way match

The three-way match is the control that ties the flow together and protects your money. Before an invoice is paid, you compare three documents:

The purchase order, which says what you ordered.
The goods receipt note, which says what you received.
The supplier invoice, which says what you are being billed.

When the quantities and prices agree across all three, the invoice is cleared for payment with confidence. When they do not, you investigate before paying. This single check catches the common problems: being billed for 100 units when only 90 arrived, a price higher than the one on the PO, or an invoice for goods that were never ordered. It is the simplest and most effective guard against overpayment and supplier errors.

PO versus invoice

The two documents are easy to confuse because they cover the same order, but they are raised by different sides at different times and serve different purposes.

In short, the PO opens the transaction and the invoice closes it. Matching one against the other, with the goods receipt in between, is what keeps the whole thing honest.

Why POs prevent disputes

Almost every supplier dispute comes down to a difference between what one side thought was agreed and what the other side delivered or billed. A purchase order removes that gap because the agreed terms are written down and numbered before anything moves. When a delivery is short, you have the PO to point to. When a price creeps up on the invoice, the PO shows the quote you both accepted. When a charge appears for an item you never ordered, there is no matching PO line, so it does not get paid.

POs also give you a clean audit trail for your accounts and your input tax credit claims, because every purchase is documented from order to payment. And they help planning: an open PO tells you what stock is on the way, which feeds directly into your reorder decisions.

Common PO mistakes to avoid

A purchase order only protects you if it is used properly. A few habits cause most of the trouble:

Raising the PO after the goods arrive. A PO written after delivery just copies the supplier's figures and gives you no protection. The whole point is to agree terms before anything moves.
Leaving prices or quantities vague. If the PO does not state an exact unit price and quantity, there is nothing firm to match the invoice against, so disputes still happen.
Skipping the goods receipt. Without recording what actually arrived, you cannot run a three-way match, and short or damaged deliveries slip through unnoticed.
Paying before matching. Clearing an invoice before checking it against the PO and the receipt is how overcharges and duplicate bills get paid.

None of these need software to avoid. They need a simple rule that the business follows every time: no order without a PO, no receipt without a check, no payment without a match.

Getting started with POs

You do not need a heavy system to begin. Start with a simple numbered PO template that captures the supplier, the items, quantities, agreed prices and delivery date. Number them in sequence so none goes missing. Record goods against the PO when they arrive, and match the invoice before you pay. As your purchasing grows, moving POs into a tool that links to your stock and billing removes double entry and keeps the whole procure-to-pay flow in one place. The discipline is what matters: agree in writing, receive against the order, match before you pay.