The difference in one line
A quotation offers a price before the work is agreed. An invoice requests payment during or after it. The quotation is the document a customer says yes to; the invoice is the one they pay.
| Feature | Quotation | Invoice |
|---|---|---|
| Purpose | Offers to supply at a stated price | Requests payment for what was supplied |
| Timing | Before the work | During or after the work |
| Creates an obligation to pay | No | Yes |
| Key date | Valid until | Due date |
| Numbering | Quotation series | Invoice series |
| Recorded as a sale | No | Yes |
| Can be withdrawn | Yes, before acceptance or after expiry | No — it is corrected with a credit note |
Why the validity date matters
A quotation is an offer. In many legal systems, once the customer accepts an offer that is still open, you are bound by it. If material prices move or your schedule fills up, an old quotation with no expiry can turn into a job you have to do at last quarter’s price. Put a valid-until date on every quotation — seven to thirty days is typical.
Turning a quotation into an invoice
Keep the same line items
Same wording, same order. A customer comparing the two documents should see the same thing twice.
Reference the quotation number
“Per quotation QUO-104 dated 12 March”. It lets whoever approves payment verify the price without contacting you.
Add variations as separate lines
Anything outside the quoted scope goes on its own line, referencing when it was authorised.
Deduct any deposit
Show it on the face of the invoice.
Set the due date
Using the terms agreed at quotation stage, not new ones.
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What a quotation needs that an invoice does not
- A valid-until date
- What is explicitly excluded — the most useful line on most quotations
- Lead time or availability
- Any assumptions the price depends on
- How to accept: signature, email reply or purchase order
- Whether it is a fixed quotation or an estimate
Common mistakes
- Sending a quotation that looks like an invoice. Head it QUOTATION and never give it an invoice number — customers have paid quotations by mistake, which creates a genuine accounting mess.
- No expiry date. Leaves the price open indefinitely.
- Quoting a single figure. Itemised lines let a customer adjust the scope instead of walking away.
- Not listing exclusions. Every unstated exclusion is a future argument.
- Invoicing something the quotation never mentioned, without written authorisation in between.
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Questions
Is a quotation legally binding?
In many legal systems a quotation is an offer, and acceptance while it is still open can form a binding contract at that price. That is precisely why a validity period matters. The specifics depend on your jurisdiction and your terms.
Can I change a quotation after sending it?
You can withdraw or revise it before it is accepted, or after it has expired. Once accepted, changing the price generally requires the customer’s agreement.
Should a quotation include tax?
Show the net, the tax and the gross separately, as you would on an invoice. A customer comparing quotes needs to know whether the headline figure includes tax.
What number should a quotation have?
Its own series, separate from invoices — QUO-001 onwards, for example. Reference that number on the resulting invoice.
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