Three documents follow every order you place. One says what you asked for, one says what actually showed up, and one says what you owe. Mix them up and you end up paying for goods that never arrived. So: the purchase order, the goods receipt note and the invoice. Who writes each one, when it turns up, and why a two-person business still wants all three.
None of this is accounting theory. It is the difference between a supplier bill you can check in ten seconds and one you pay because arguing about it feels like more effort than it is worth. Every business that buys anything from anyone produces these three records, whether or not it calls them by these names.
The three documents at a glance
The whole idea fits in one table. Read it left to right and you have the shape of every purchase you will ever make.
| Document | Who issues it | When | What it proves |
|---|---|---|---|
| Purchase order (PO) | You, the buyer → to the vendor | Before anything moves | What you asked for, at what price, by when |
| Goods receipt note (GRN) | You, the buyer → for your own records | The moment goods arrive | What actually arrived, in what condition, and who checked it |
| Invoice | The vendor → to you | After dispatch or delivery | What the vendor says you owe, and by when |
Notice who owns what. Two of the three are yours. The invoice, the only one of them that asks you for money, is the one you did not write, and that asymmetry is the entire reason the other two exist.
What is a purchase order?
A purchase order is your request to a vendor, written down before the goods move. It flows buyer to vendor and it answers one question: what did I ask for?
A usable PO carries five things. Nothing beyond them is essential:
- Who you are ordering from, the vendor and ideally the person you dealt with
- What you want, in item names specific enough that nobody has to guess
- How much, as quantity and unit (kg, boxes, pieces, metres)
- At what price, meaning the agreed unit rate, not “usual rate”
- By when, the expected delivery date
Everything else on a formal PO template (terms and conditions, signature blocks, GST details, delivery addresses) is useful without being the thing that makes the document work. The five items above are what you will argue from later.
Your real purchase order is probably a WhatsApp message
Most small businesses never raise a PO on letterhead. They type into a chat window: “Bhai, 30kg Arabica, same as last time, Friday morning please.” And honestly, that works. A purchase order is a record of intent rather than a legal form, and a dated message from your number to the vendor’s number is a record of intent.
The format was never the problem. Findability is. A message only counts as a purchase order if you can produce it three weeks later, in under a minute, without scrolling past four hundred other messages. That is the bar. Fail it and what you actually have is a memory with a timestamp buried somewhere you cannot reach.
Two habits fix most of it. Write the order as one self-contained message instead of spreading it across six back-and-forth lines. Then copy the same five details somewhere outside the chat: a sheet, a notebook, an order board. There is a lot more on this in how to track vendor orders on WhatsApp.
What is a goods receipt note (GRN)?
A goods receipt note is your record of what actually arrived. You write it, at the moment of delivery, for yourself. It answers: what did I receive?
You will also hear it called a delivery receipt, a goods received note, or a purchase receipt. In India it sits alongside the vendor’s delivery challan, which is a different animal: the challan is what the vendor says they sent, the GRN is what you say you got. When those two disagree, the disagreement is the whole point.
A GRN records, per item:
- The date and time goods arrived
- Which order it relates to
- Quantity ordered vs quantity actually received
- Condition: damage, wrong item, wrong grade, short weight
- Who received and checked it
That last line matters more than people expect. Who signed for it is the difference between a fact and an argument. If the driver left 42 bags and your evening staff member counted them, write the name down. A month later that name is the only thing standing between you and paying for eight bags of nothing.
Partial deliveries are where the GRN earns its keep, and they are common enough to deserve their own article. What a goods receipt note is, and how partial deliveries work covers the mechanics of running a received-vs-ordered balance.
What is an invoice?
An invoice is the vendor’s request for payment. It flows vendor to buyer, usually after dispatch or delivery, and it answers: what do I owe?
A normal invoice shows:
- The vendor’s details and yours
- An invoice number and date
- Line items with quantities and rates
- Taxes, if applicable
- The total, and payment terms: due on receipt, 15 days, 30 days
The bit worth internalising is that an invoice is a claim, not a fact. It is written by the person who wants the money, from their own records, often by someone in their office who never saw the truck. It can be right. It can also bill you for the full quantity when only part of it turned up, quote last quarter’s higher rate, or arrive twice for the same delivery. None of that requires anyone to be dishonest. Busy offices make ordinary mistakes.
You do not check an invoice by looking at it harder. You check it against the other two documents. That comparison has a name, three-way matching, and it is the only reliable way to know a bill is correct before you pay it.
How they work together
One ordinary example. A café orders coffee beans.
Monday: the purchase order
The owner messages the roaster: 30kg of the house blend at ₹720/kg, delivery Thursday morning. The roaster replies “confirmed”. That exchange is the purchase order. Thirty kilos, ₹720, Thursday. Expected total: ₹21,600.
Thursday: the goods receipt note
The van arrives at 7:40am. The barista opening the shop counts the sacks: five sacks of 5kg each. That is 25kg, not 30. The driver shrugs, because the roaster had a short batch. She photographs the delivery note, writes “25kg received, 5kg short, driver informed, checked by Anjali, 7:40am” against the order, and gets on with opening up.
Thirty seconds of work. That thirty seconds is the whole article.
The following week: the invoice
The roaster’s invoice lands by email: 30kg at ₹720, total ₹21,600. Their office billed from the order rather than from what the van actually carried. Nobody lied. The dispatch note simply never reached the person raising invoices.
The match
Now line up all three:
| Source | Quantity | Amount |
|---|---|---|
| Purchase order (what you asked for) | 30kg | ₹21,600 |
| Goods receipt note (what arrived) | 25kg | ₹18,000 at the agreed rate |
| Invoice (what you are being asked to pay) | 30kg | ₹21,600 |
The gap is ₹3,600 and it shows up in about four seconds. The café owner sends one message: “Only 25kg came Thursday, Anjali signed for five sacks. Can you send a revised invoice, or ship the 5kg balance?” The roaster either credits the difference or delivers the rest. Either way the conversation stays short, unemotional and factual, because there is a record behind it.
Without the GRN, that same conversation is two people remembering a Thursday differently. Most owners, faced with that, pay the ₹3,600. Do it eight times a year and the arithmetic gets uncomfortable.
Do small businesses really need all three?
Honest answer: you need the information, not the paperwork.
Nobody is asking a twelve-seat café to run a formal three-document workflow with printed PO numbers. What you need is to be able to answer three questions about any order quickly, from a record rather than from memory:
- What did I ask for, at what price?
- What actually arrived, and who checked it?
- What am I being charged?
A WhatsApp message, a photo of the delivery note with counted quantities written on it, and the vendor’s bill will answer all three, provided they are linked together. That word is doing the heavy lifting. Three pieces of evidence scattered across a chat thread, a phone gallery and an email inbox are not a system. The same three hanging off one order record are.
So the real division is linked versus scattered, and it has very little to do with how much paperwork you generate. Whether you link them with a shared spreadsheet, a physical file per vendor, or an order board like OrderBookApp where the delivery and invoice hang off the original order matters far less than whether you link them at all.
What “good enough” looks like by size
- A few orders a week with one person ordering: a clean order message, a delivery photo with counts written on it, and a folder of vendor bills. Review it weekly.
- Once ten or more orders are open and two people are placing them, memory stops working and you need a shared record with statuses. A spreadsheet at minimum. See spreadsheet vs software for PO tracking.
- If partial deliveries or disputed invoices are routine, you need per-item received quantities recorded against the order, and that is the point where a sheet starts to strain.
Keep reading
- What is a goods receipt note (GRN)? Partial deliveries explained. The document most small businesses skip, and the one that catches short deliveries.
- Three-way matching for small businesses. How to use all three documents together before you pay anything.
- The vendor order lifecycle: 7 stages from placed to paid. Where each document fits in the life of an order.
Frequently asked questions
Is a WhatsApp message a valid purchase order?
For everyday buying, yes. Commercially it holds up. A dated message that states items, quantities, agreed price and delivery date, sent from you to the vendor, is a written record of what you ordered, and a vendor’s reply accepting it is evidence they agreed.
Two caveats. It only counts if you can find it later, because an order you cannot retrieve in a minute is not functioning as a record. And if you are buying something high-value, or your vendor contract or tax position calls for a formal document, raise a proper PO. For a café ordering beans or a shop reordering stock, the message is fine.
Can the invoice amount differ from the PO?
Yes, and it legitimately does all the time. Common honest reasons: only part of the order was delivered, an agreed rate changed before dispatch, freight or packing was added, taxes were calculated differently, or you asked for extra items after the original message.
So the useful rule is a looser one than “the invoice must match the PO”. Any difference should have an explanation you accept, and the quantity billed should match what your goods receipt note says arrived. A difference with a reason is fine. A difference nobody can explain is the one to hold.