These four documents get used interchangeably in conversation and that's where the trouble starts — a client asking for "an invoice" when they mean a quote, or a contractor calling a receipt an invoice because it's the only word they reach for. Each one has a specific job, and using the wrong one can cost you: an estimate sent as an invoice looks like you're billing for work you haven't done yet.
A quote or estimate comes first. It's what you send before the work starts, so the client knows roughly (estimate) or exactly (quote) what they'll owe. Neither is a bill — no payment is due, and neither should look like one.
Once the client accepts, the estimate or quote converts into an invoice: now it is a bill, with a due date and payment terms. This is the document that actually asks to be paid.
A receipt comes last, and only after money has changed hands. It doesn't stand alone — it documents a specific payment against a specific invoice. "Make me a receipt" with nothing to attach it to isn't a real request; it's asking for proof of something that didn't happen.
The shorthand: quote/estimate → invoice → receipt. Same underlying document, moving through its life. Converting one into the next — rather than retyping it — is what keeps the numbers, dates, and client details from drifting apart along the way.
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