Invoice vs Quote vs Estimate: What's the Difference?

A quote says "this is what it will cost." An estimate says "this is roughly what it will cost." An invoice says "this is what you owe, please pay." They happen in that order, and each one should agree with the one before it.

	Estimate	Quote	Invoice
Timing	Before work	Before work	After work (or at milestones)
Price	Approximate	Fixed for the defined scope	Final amount due
Can change?	Yes, within reason	Only if scope changes	Only by credit note
Expires?	Often	Yes, set a validity date	No; it has a due date
Asks for payment?	No	No (deposit terms aside)	Yes

Quotes

A quote is a fixed price for a clearly defined job. If the client accepts it, you're generally expected to honor that price. In many places an accepted quote can form a binding contract.

That's why a good quote includes:

• Exactly what's included, in enough detail that there's no argument later
• What's excluded: "Does not include disposal of old units"
• How changes will be priced: "Additional work at $75/hour, agreed in writing"
• A validity date: "Valid for 30 days"
• Payment terms, including any deposit

Estimates

An estimate is your informed best guess when you can't know the full scope yet. A plumber who hasn't opened the wall, a developer asked to "fix some bugs", a painter who hasn't seen the damp. It signals that the final price may move.

Say how much it might move and why. "Estimate based on 2 days of work; if the subfloor needs replacing, we'll stop and give you a quote before continuing" is honest and protects both sides. In some trades and places, consumer-protection rules limit how far a final bill can exceed a written estimate without the customer's approval; auto repair in several US states is a common example. See car repair invoices.

Invoices

The invoice comes after the work (or at agreed stages). It should match the accepted quote, or the estimate plus any agreed changes. If it doesn't, explain the difference on the invoice itself:

Kitchen tiling as quoted (Q-0112): $2,450.00 Additional: replace damaged backer board, agreed by phone 12 Sept: $380.00

Anything that looks like a surprise on an invoice slows payment down.

How the three connect

1. You send an estimate or quote, numbered in its own series (EST-0021, QUO-0104).
2. The client accepts it, ideally in writing.
3. You may send a deposit invoice if your terms include one.
4. You do the work.
5. You send the invoice, quoting the quote number as a reference, minus any deposit paid.

In the generator you can do this without retyping: create the quote, download it, then switch the document type to Invoice when the job's done. The line items, client and branding all carry over.

Common questions

Can I charge more than my quote? Only if the scope changed and the client agreed. Get that agreement in writing before doing the extra work.

Do quotes need tax on them? If you're registered for VAT, GST or sales tax, yes: show it separately so the client knows the total cost.

Should quotes and invoices share numbers? No. Keep separate series so unaccepted quotes don't leave gaps in your invoice sequence. See invoice numbering.

What's a proforma invoice, then? It's closer to a quote in invoice format, used mainly in trade and for advance payments. See proforma invoices.