Blog · October 2026 · 5 min read

Quotation vs estimate vs proforma invoice: what's the difference?

Q: What is the difference between a quotation and an estimate?

A quotation is a fixed, binding offer: accept it and you generally must honor the price. An estimate is an educated guess that may change as the work becomes clear. Use quotes when the scope is fixed, estimates when it is not.

Q: What is a proforma invoice?

A proforma invoice is a preliminary bill sent before work starts or goods ship, often to request an advance payment or clear customs. It is not a demand for payment like a real invoice and usually cannot be used for tax purposes.

Q: How do I convert a quote into an invoice?

In the free invoice generator on this site, open any accepted quotation and click Convert to invoice. Customer, items, taxes and notes carry over with a fresh invoice number.

Q: Should I send a quote or an invoice first?

Quote first, invoice after. The quote agrees the price, the work happens, then the invoice demands payment referencing the accepted quote.

Send the wrong pre-invoice document and you either scare the client off or lock yourself into a price you cannot keep. Here is the 60-second version, then the details.

The short answer

Quotation: a fixed price offer. Accepted means you honor it. Use when scope is fully known.
Estimate: an educated guess. The final figure may move as unknowns resolve. Use for exploratory work.
Proforma invoice: a preliminary bill before work or shipment, often to unlock an advance payment. Not a tax document in most jurisdictions.

When to send each

Exploratory project? Send an estimate with the assumptions listed, so changes feel fair, not sneaky.
Fixed scope, agreed price? Send a quotation with an expiry date (14 to 30 days is standard).
Need money up front? Send a proforma invoice referencing the accepted quote.
Work accepted? Convert the quote into a real invoice. In our free generator this is one click: customer, items, taxes and notes carry over with a fresh number.

The expensive mistakes

Quoting a guess. If the scope can move 30 percent, that document should have been an estimate. Fixed quotes on fuzzy scope are how freelancers work for free.
No expiry date. A quote without expiry is an open-ended promise. Always date it.
Re-typing the invoice. Every manual re-entry is a chance to mistype a price or tax. Convert, don't recreate.

Do it free in one flow

Create the quote with an expiry date and terms, get it accepted, convert it to an invoice, download the PDF. No account, no watermark, in 9 languages.

Make a free quotation

Quote FAQ

What is the difference between a quotation and an estimate?

A quotation binds you to a fixed price; an estimate is a guess that may change. Fixed scope gets a quote, fuzzy scope gets an estimate.

What is a proforma invoice?

A preliminary bill before work or shipment, often for advance payment or customs. Generally not a tax document.

How do I convert a quote into an invoice?

Open the accepted quote and click Convert to invoice. Everything carries over with a new number.

Should I send a quote or an invoice first?

Quote first to agree the price, invoice after the work to demand payment.