Quote, estimate, pro forma and invoice: what's the difference

Quotes, estimates, pro forma invoices, purchase orders and invoices show up in almost every business sale, and people often use them interchangeably. They aren't the same: each one appears at a different point in the sale, and only one — the invoice — is a tax document.

It's the document where you propose a price before selling: what you'll deliver, how much it costs, on what terms and until when. It doesn't oblige the client to pay and has no tax value.

What it does is put your offer in writing. When the client accepts it — ideally by signing it — there's a record of what you both agreed: scope, price and terms.

In practice, almost always. Some trades use “estimate” for work whose final cost can vary — construction, repairs — and “quote” for fixed-price products, but there's no single rule: what matters is what the document says, not what it's called.

If your estimate can change, say so in writing: “the final amount may vary by up to 10% depending on materials.” That one line prevents most complaints.

It has the format of an invoice — tax details, line items, taxes — but it's a preliminary document. It's used so the client can arrange an advance payment, financing or an import, and it doesn't replace the tax document. If you issue one, label it clearly as “pro forma.”

It's the client's internal confirmation that they'll buy what you quoted. Many mid-size and large companies require one before paying. If your client works that way, ask them to reference your quote number on it: the two documents stay linked and nobody argues about what was ordered.

It's the only one of these documents with tax value, and in most Latin American countries it's now electronic and issued under the tax authority's rules: Mexico's CFDI stamped with the SAT, Colombia's DIAN-validated e-invoice or Peru's SUNAT electronic receipt, for example. It's issued when the sale or payment happens, according to each country's rules.

That's why signing a quote, however formal, never turns it into an invoice. They complement each other: the accepted quote backs up what you'll invoice later.

1. You send the quote. 2. The client accepts and signs it (and, if their company requires it, issues a purchase order). 3. You collect the deposit, if one was agreed. 4. You deliver the product or the work. 5. You issue the invoice.

The step most often skipped is the second. Without written acceptance, if there's a disagreement about scope or price at the end, it's one person's word against the other's.

Firmiu handles the quote and its acceptance: you build it with your details and catalog, send it to sign, and the client accepts it from their phone, with a certificate that records who signed and when. It doesn't issue invoices — each quote's PDF says so — so you keep issuing invoices in the system your country's tax authority requires.