Invoice, receipt, quote or purchase order: which to send when

Here is the short answer. A quote proposes a price, a purchase order commits to that price, an invoice asks for the money once the work is done, and a receipt proves the money arrived. Line them up in that order and they stop being confusing, because each one belongs to a different moment in the same deal.

They look almost identical on the page. Same logo, same list of items, same prices. That is exactly why people mix them up. But the layout is not what tells them apart. What tells them apart is when they appear and who sends them.

TL;DR: Quote, then purchase order, then invoice, then receipt. The seller issues three of them; the buyer issues only the purchase order. The one distinction people bury: an invoice requests payment (money still owed), a receipt proves payment (money already paid).

Follow one order through all four documents

Say you run a small print shop. A customer wants 500 flyers. Here is every document that changes hands, in order.

Step one, the quote. You issue it. You send the customer a quote: 500 flyers, full colour, 120 pounds, valid for 30 days. Nobody has committed to anything yet. You are proposing a price so the customer can decide.

Step two, the purchase order. The customer issues it. They like the price and send back a purchase order, PO-4471, saying “yes, print the 500 flyers at 120 pounds”. Now there is a commitment. Notice the direction flipped: the seller proposed, the buyer accepted in writing.

Step three, the invoice. You issue it. You print the flyers, deliver them, and send an invoice: 120 pounds, due in 14 days, referencing their PO-4471. The invoice is a request. The money is still owed at this point.

Step four, the receipt. You issue it. The customer pays the 120 pounds. You send a receipt confirming you received it. The money has now changed hands, and the receipt is the proof.

Same customer, same 500 flyers, same 120 pounds, running through four documents. The only thing that changes is what stage of the deal you are in.

Who issues what, and why it trips people up

Count the issuers in that story and something jumps out. The seller sent three of the four documents: the quote, the invoice, and the receipt. The buyer sent exactly one: the purchase order.

That is the detail most people get backwards. They assume the buyer sends a lot of paperwork, when really the buyer’s only formal document is the PO. Everything else flows from the seller. If you sell, you spend most of your time on the seller’s three. If you buy, the one document you originate is the purchase order.

A quote proposes a price before any work starts

A quote is the first document in the chain, and the seller issues it. You send it to a prospective customer to say “here is what this will cost”, before anyone has committed. It lists the work or goods, the price per line, and usually a date the price is valid until. Its job is to win the work and set expectations so there are no arguments about cost later.

The word matters. A quote is normally a firm price you will stand behind, while an estimate is your best guess that may move as the job becomes clearer. Both use the same layout, so spell out which one you mean if there is any doubt. A “valid until” date protects you, because it stops a customer accepting a months-old price after your own costs have gone up.

A purchase order commits the buyer to that price

A purchase order, or PO, flows the other way. The buyer sends it to you to commit to the goods or services at the agreed price. It carries a unique PO number and lists exactly what is being ordered. Where a quote says “here is what it would cost”, a purchase order says “yes, supply this”.

Not every deal needs one. A freelancer working with an individual rarely sees a PO at all. But larger organisations use them to approve spending internally before any money is committed, and they expect that PO number to appear on your later invoice so the two can be matched. If a client asks you to put their PO number on your invoice, this is why.

An invoice requests payment once the work is done

The invoice is the document most people picture, and the seller issues it. You send it after the work is delivered to ask for payment. It should leave no room for confusion, so a clear invoice carries your details and the customer’s, a unique invoice number, the issue and due dates, an itemised list with quantities and rates, any tax, the total owed, and how to pay.

Here is the part to hold onto: an invoice is a request. When you send it, the money is still owed. That is what separates it from the receipt, which we will get to next. People treat the two as the same document because the line items match, but one asks and the other confirms.

Numbering is the piece people overlook. A simple running sequence such as INV-0001, INV-0002 keeps every invoice unique and in order, which matters for your records and for tax. Some businesses fold in the year or a client code, like 2026-014. The scheme is yours to choose, as long as no two invoices ever share a number.

A receipt proves the payment was made

A receipt is the last link, and the seller issues it too. Once the customer has paid, you give them a receipt as proof the money was received. It shows who issued it, who paid, the date, what was paid for, the amount, and ideally the payment method.

This is the cleanest way to tell a receipt from an invoice, and it is the distinction most guides skip past. An invoice asks for money that is still owed. A receipt proves money that has already been paid. If you are ever unsure which of the two you are looking at, ask one question: has the money moved yet? Before it moves, it is an invoice. After it moves, it is a receipt.

Receipts matter most for payments with no card slip behind them, cash and bank transfers especially. A dated receipt gives both sides a record they can keep, which heads off the awkward “did you ever pay me for that” conversation. For rent, deposits and one-off charges, it is often the only proof either party will hold.

Reading the chain in order

Lined up in the order they travel, the four stop being interchangeable: quote, purchase order, invoice, receipt. The first two happen before the work, the last two after. Watch the money too: the invoice comes while it is still owed, the receipt comes once it has been paid. Once you can place a document in that sequence, picking the right one is almost automatic.

If you raise these documents by hand, the invoice and billing tools build each of the four from one form, with your logo and a clean PDF, so the layout stays consistent and only the purpose changes.