Invoice vs Receipt vs Quote vs Estimate: Which Do You Send?

A client emails asking for “an invoice so we can get this approved”. The work has not started. You have not agreed a price. What they actually want is a quote, or possibly a proforma, and if you send a real invoice you have just recorded a sale that has not happened.

This confusion is everywhere, and it is not because people are careless. The documents look almost identical. They carry the same logo, the same line items, the same totals. What separates them is what they do, and that is invisible on the page unless somebody labels it properly.

Getting invoice vs receipt vs quote vs estimate straight is worth an afternoon of your life because each mistake has a specific cost. Send a quote that reads like an invoice and a client may treat it as a bill and dispute it. Miss a purchase order number and your invoice sits in a queue for six weeks. Treat a proforma as income and your accounts overstate a year that has not happened yet.

Eight documents, then. What each does, who issues it, and the order they run in.

The short answer

Think of each document as answering one question.

An estimate answers “roughly what will this cost?” and is deliberately not binding. A quote answers “what exactly will this cost?” and normally becomes binding once the client accepts it. A purchase order is the buyer saying “we authorise this spend”, and its number usually has to appear on your invoice. A proforma invoice says “please pay before we supply” and is generally not a tax document. An invoice says “you owe this, here is when to pay” and is the tax document. A receipt says “we got the money”. A credit note says “part or all of that earlier invoice is cancelled”. A statement of account says “here is everything still outstanding”.

The tax treatment of several of these differs by country and changes, so check the position with HMRC, the IRS, the GST portal, the ATO, the CRA or your accountant before you rely on it.

The documents, side by side

Here are the eight, plus two more you will run into occasionally.

Two of those are worth flagging because freelancers rarely meet them. A remittance advice arrives from the client’s system and tells you a single payment of £9,120 covers invoices 041, 047 and 052, which saves you an hour of reconciliation. A delivery note only matters if you ship physical goods.

Estimate and quote: the difference that costs money

An estimate is your considered guess before the job is fully defined. A quote is a price you are committing to.

Most guides stop there. That is roughly right and it is also too simple, because the heading on the document is not what decides which one you have given. The words inside it are. I have seen documents headed “Estimate” that state a single precise figure with no assumptions and no caveats, and a client can reasonably read that as a price they are being offered.

So write estimates like estimates. Give a range rather than a point: “£5,800 to £7,000 depending on the number of packaging variants”. List the assumptions you priced against. State plainly that the figure is indicative and will be confirmed by a quote once the scope is agreed. Put an expiry on it anyway, because material costs and your own availability move.

And write quotes like quotes. One number, or a clearly itemised set of numbers that add to one number. What is included, and just as usefully what is excluded. How long you will hold it for. What happens if the scope changes, which is normally a variation priced separately rather than absorbed. Payment terms and any deposit, because agreeing the price without agreeing the payment structure is how projects end up funded entirely by you.

If you build these regularly, the Project Estimate Builder is set up for the ranged, assumption-listing version and the Project Quote Builder for the fixed-price one. Keeping them visually distinct is half the battle: if your estimate and your quote look identical, nobody downstream will treat them differently either.

Is a quote legally binding?

Generally, yes, once accepted, and I want to be careful here because this is a genuine legal question rather than a formatting one.

The usual analysis in common-law systems is that a quote is an offer. When the client accepts it on the stated terms, and there is consideration on both sides, you have a contract at that price. That is why a quote should carry an expiry: an offer left open indefinitely can be accepted at a moment when it no longer works for you. “This quotation is valid for 30 days from the date above” is one sentence and it does a lot.

Where it gets murkier. Acceptance has to be of your terms, and if the client responds with a purchase order carrying their own standard terms on the back, you may be in the classic battle of the forms, where whose terms govern is a real dispute rather than a technicality. An estimate that is worded like a fixed price can be argued to be an offer regardless of its heading. And a quote given verbally on a phone call is not automatically worthless, which cuts both ways.

None of this is legal advice, the position varies by jurisdiction, and if a serious sum is at stake you want an hour with a solicitor rather than an afternoon with search results. What you can do without advice is make your documents unambiguous: heading, expiry, inclusions, exclusions, assumptions, and a line stating which terms of business apply.

Proforma invoices, and why they are not income yet

The proforma is the document I would most like freelancers to use more and misuse less.

A proforma invoice is a request for payment issued before you supply. It looks like an invoice, it carries the same details, and it usually says PROFORMA across the top. It exists for three common situations: taking a deposit, dealing with a new client you would rather not extend credit to, and shipping goods across a border where customs needs a declared value before the real invoice exists.

What makes it different is that in most tax systems it is not a tax invoice. It does not create a tax point, the buyer generally cannot use it to reclaim VAT or GST, and you generally should not post it as a sale. It is a polite, formal “please send money and then we will do the paperwork properly”.

The sequence that trips people up is what happens after it is paid. Once the money arrives, you issue a real invoice for the same amount, and that invoice is the tax document. Skipping this step is the single most common proforma error, and it produces an awkward gap where money has been received against nothing that counts as a sale.

The received wisdom on this does not hold up on common advice. Plenty of guidance tells freelancers to simply raise a normal invoice for the deposit and be done with it, and for a sole trader who is not registered for any consumption tax that is genuinely fine and simpler. If you are VAT or GST registered, the choice between a proforma and a straight deposit invoice affects when tax becomes due, and the answer depends on your country’s tax point rules. Ask your accountant once and then do it the same way forever. Our piece on adding VAT or GST to a freelance invoice goes into the mandatory fields in more depth.

Give proformas their own number series, such as PRO-2026-003, kept separate from your invoice run. Mixing them in creates gaps in the invoice sequence that you then have to explain.

The purchase order, and the number that gets you paid

A purchase order is issued by the buyer, not by you. It is their internal authorisation, usually created after they accept your quote, and it carries a number.

That number is the most practically valuable string of characters in this entire article. At most mid-sized and large organisations, accounts payable matches incoming invoices against open purchase orders automatically. Your invoice with the right PO number matches, gets approved, and enters a payment run. Your invoice with no PO number, an old PO number, or a PO number formatted slightly differently does not match, and in many systems it does not generate a helpful email either. It just sits.

So ask for it before you start work, not when you invoice. “Do you need to raise a PO for this, and can you send me the number when you do?” is a normal question that makes you look like you have done this before.

Watch the value on the PO as well. If the PO is raised for £6,400 and you invoice £6,900 because of an agreed variation, the invoice can fail the match on amount even with the right number. Variations need the PO amending, which the buyer has to do. Chase that at the time rather than at the point of invoicing.

The difference between a purchase order and an invoice, in one line: a purchase order is the buyer promising to spend, and an invoice is the seller asking to be paid. They point in opposite directions and both usually carry the same reference number.

Invoices, receipts and remittance advice

An invoice is a demand for payment under an agreement that already exists. It is also, in most systems, the tax document: the thing that records the sale, states the tax charged, and lets a registered buyer reclaim it. That is why the required fields are prescribed and why a missing element can make it invalid.

A receipt confirms money arrived. It is not a demand, it creates no obligation, and it usually is not the tax document itself. In consumer settings the receipt often doubles as the record of sale, which is where the confusion comes from.

Should you send receipts? The standard advice is to always send one, and for business-to-business work I think that is mostly noise. Your client has a bank statement and your invoice; a third PDF adds nothing and nobody files it. Send a receipt when the client pays by card or cash, when they are an individual rather than a company, when the payment is a deposit that a later invoice will draw down, or when they ask. Those four cases cover almost everything real.

Remittance advice runs the other way. The client’s system sends it to say which invoices a payment covers. If you get paid a single lump sum by a larger client and cannot work out which invoices it settles, ask their accounts payable team to send remittance advice with payments. Most can switch it on in one click, and it removes a recurring hour of guesswork.

Whichever of these you are producing, the header has to say what it is, in large type. A document headed INVOICE gets processed as an invoice. A document with no heading gets processed as whatever the recipient assumes. Building the document in the ToolFiddle invoice generator means the heading, the numbering and the totals are handled for you, and because it runs in your browser, the client details and amounts never leave your machine.

Credit notes and refunds are not the same thing

A credit note is paperwork. A refund is money. Confusing them is where small businesses create genuinely messy accounts.

If you invoiced £3,840 and one deliverable worth £600 was dropped, you issue a credit note for £600 against that invoice. The client now owes £3,240. No money has moved in either direction. If the client had already paid the full £3,840, you would issue the same credit note and then separately refund £600, and those are two events with two records.

The rule underneath is simple: once an invoice has been issued and sent, do not change it. Correct it with a credit note. This holds even when the error is embarrassing and entirely yours, and it holds especially when tax has been charged, because the mechanism for unwinding tax already declared is a credit note rather than a quiet edit. Confirm the timing with your accountant, since the rules on adjusting a filed return differ by country.

Credit notes should carry their own numbering series and reference the original invoice number explicitly. If you have not settled on a numbering approach yet, our guide to invoice numbering systems covers how to run parallel series without creating gaps you cannot explain.

A statement of account is the last piece. It is a summary you send to a client showing every invoice outstanding, the dates, the amounts and the total. It is not a demand for any specific invoice and it is not a tax document. It is useful with clients who owe you across several invoices and have lost track, and it is a gentle way of raising the subject: “here is where we are” rather than “you are late on invoice 47”.

Worked example: one £6,400 rebrand from start to finish

Say Ellis is a freelance brand designer in Bristol working with a coffee roastery. Here is every document, in order, with the numbers.

1. 4 February, estimate EST-2026-011. The roastery has a rough brief and no fixed scope. Ellis sends an estimate of £5,800 to £7,000, listing assumptions: three packaging variants, one round of revisions, no photography. It states in bold that it is indicative and not an offer, and that it lapses on 6 March.
2. 18 February, quote QUO-2026-006. Scope agreed. Ellis sends a fixed quote of £6,400, itemised as identity £3,200, packaging £2,400 and guidelines £800. Included and excluded are listed separately. Valid until 20 March. Terms: 40% deposit, balance on delivery, Net 14.
3. 25 February, acceptance. The roastery replies “approved, please proceed” and raises purchase order PO-88412 for £6,400. Ellis saves the PO and notes the number where the invoicing details live.
4. 26 February, proforma PRO-2026-003. The 40% deposit is £6,400 × 0.40 = £2,560. Ellis sends a proforma for that amount, clearly headed, quoting PO-88412, and does not record it as a sale.
5. 2 March, payment and invoice INV-2026-041. The £2,560 lands. Ellis now issues a proper invoice for £2,560 against the proforma, and this is the document that goes into the books. A receipt, REC-2026-018, goes out the same day because it is a deposit that a later invoice will draw against.
6. 10 April, delivery and final invoice INV-2026-052. Balance is £6,400 minus £2,560 = £3,840. The invoice quotes PO-88412, references INV-2026-041 for the deposit already paid, and states Net 14 with a due date of 24 April.
7. 14 April, scope change and credit note CN-2026-002. The roastery drops one packaging variant, agreed at £600. Ellis issues a credit note for £600 referencing INV-2026-052. The invoice stays exactly as it was.
8. 22 April, payment. The roastery pays £3,840 minus £600 = £3,240 and sends remittance advice confirming it settles invoice 052 net of credit note 002.

Check the arithmetic end to end. Received: £2,560 + £3,240 = £5,800. Quoted: £6,400. Credited: £600. And 6,400 minus 600 is 5,800, so the books close.

Eight documents for one job sounds like bureaucracy. In practice steps 1 and 8 are optional, step 4 collapses into step 5 for a lot of freelancers, and the whole sequence takes maybe forty minutes of admin across three months. What it buys you is that at no point does anyone have to remember what was agreed. If you need to archive the whole trail afterwards, PDF Merge will collapse those files into one document per project, which is far easier to find in two years than eight attachments across two email threads.

The four ways this goes sideways

Sending a quote that reads like an invoice is the classic. It has your bank details on it, a total, and no expiry, and the client’s finance team enters it as a payable or, worse, queries it as an unexpected bill. Quotes should not carry payment instructions. Save those for the invoice.

Missing the PO number costs more weeks than any other single error on this list, and it is entirely preventable by asking one question at the start.

Treating a proforma as income overstates your revenue and can create a tax position that does not reflect what actually happened. Keep proformas out of your sales figures until the real invoice exists.

Refunding by editing the original invoice is the accounting equivalent of tidying up by hiding things in a drawer. It works right up until someone opens the drawer.

Sending a receipt instead of an invoice happens more than you would think, usually when a client pays a deposit and the freelancer marks the payment with a “receipt” and never raises the invoice. The money is in the bank and there is no sales document behind it.

Then there is the documentation gap around variations. A quote covers what it covers. When the client asks for a fourth packaging variant in week six, the correct move is a short written variation, priced, agreed by email, before you do it. The number of freelancers who absorb scope creep because raising it felt awkward is very large, and the awkwardness of asking in week six is nothing compared to the awkwardness of invoicing for it in week ten.

One more, quieter than the rest: no expiry on quotes. A client accepting a quote you sent eleven months ago, at prices you no longer charge, is not a hypothetical. Thirty days is a normal window and nobody blinks at it.

Finally, watch the currency and the tax status on documents that cross borders. “$6,400” is ambiguous, and a document that does not say whether tax is included, excluded or not applicable will be read the way that suits the reader. Say it explicitly. If you scan or photograph signed acceptances, Image to PDF will turn them into something filable rather than leaving them as photos in your camera roll.

Frequently asked questions

What is the difference between a quote and an estimate?

A quote is a fixed price you are offering to hold, usually for a stated period. An estimate is your honest guess at a likely cost, given before the scope is settled, and it should say on its face that it is not binding. The wording on the document matters more than the heading, so put the range, the assumptions and the expiry in writing.

Is a quote legally binding?

A quote is generally treated as an offer, and once the client accepts it on the stated terms you usually have a contract at that price. Whether that holds depends on the wording, on what the client actually agreed to, and on the law where you trade. Add an expiry date and list your assumptions, and take proper advice before relying on it in a dispute.

What is a proforma invoice used for?

A proforma is a request for payment issued before supply, most often for deposits, new clients and cross-border shipments where customs needs a declared value. It is generally not a tax invoice and normally should not be entered as a sale or used by the buyer to reclaim tax. Once it is paid, issue a proper invoice for the same amount.

Do I need to send a receipt if the client has a bank transfer record?

For most business-to-business work, no. The bank record plus your invoice is enough, and clients rarely ask. Send one anyway when a client pays by card or cash, when they are an individual rather than a company, when the payment is a deposit against a later invoice, or when anyone asks. It takes a minute and prevents queries.

What is the difference between a credit note and a refund?

A credit note is the paperwork that reduces or cancels an invoice. A refund is the money going back. You can issue a credit note without refunding anything, for example when a client still owes you more than the credited amount and you simply reduce the balance. Never fix an overcharge by editing the original invoice.

Why does my invoice need a purchase order number?

Because at most mid-sized and large companies the purchase order is what authorises the spend, and their accounts payable system matches invoices to it automatically. An invoice with no PO number, or the wrong one, often fails that match and stops without anyone telling you. Ask for the number before you start work and print it on every invoice.

Putting it to work this week

Look at whatever you last sent a client and ask which of the eight it actually was. If the heading and the contents disagree, fix the template rather than the individual file.

Three changes will cover most of it. Put an expiry date on every quote and a not-binding line on every estimate. Ask for a purchase order number on the first call with any client big enough to have one, and print it on every invoice you send them. And when something needs correcting, reach for a credit note rather than the original file.

The invoice generator will produce the invoice, proforma or credit note with the right heading and numbering already in place, so the only thing left to get right is which document you meant to send. That decision is yours, and now you have the map for it.