Two Documents, Very Different Jobs
A proforma invoice is a quote dressed up as an invoice. A commercial invoice is a demand for payment. They look almost identical — same fields, same layout — but they serve completely different purposes, and confusing the two causes real problems.
The proforma says "this is what it will cost." The commercial invoice says "you owe this." One comes before the deal is finalised; the other comes after goods ship or services are delivered. Mixing them up can mean a client pays an estimate instead of the final amount, or customs holds a shipment because you attached a proforma instead of a proper commercial invoice.
What a Proforma Invoice Actually Is
A proforma invoice is a preliminary document that outlines the expected cost of goods or services before a transaction is confirmed. It is not a demand for payment. It is not recorded as revenue in your books. It is not a tax document.
Think of it as a formal quotation. Clients use proforma invoices to:
- Secure budget approval internally — the proforma gives their finance team the numbers they need to sign off before committing.
- Arrange payment in advance — common in international trade where the seller requires prepayment.
- Clear customs (in some cases) — customs authorities may accept a proforma for estimating duties on pre-shipment goods, though a commercial invoice is required for the actual clearance.
- Apply for import licences or letters of credit — banks and trade authorities often require a proforma as part of the application.
A proforma should be clearly labelled "PROFORMA INVOICE" at the top. This is not optional — unlabelled proformas get mistaken for commercial invoices and processed for payment at the wrong amount.
Side-by-Side Comparison
| Feature | Proforma Invoice | Commercial Invoice |
|---|---|---|
| Purpose | Estimate / quotation | Demand for payment |
| Legally binding? | No (it's an offer) | Yes |
| Triggers payment? | No | Yes |
| Recorded as revenue? | No | Yes |
| Has a unique invoice number? | Optional (use a PI- prefix) | Required (sequential) |
| Used for customs clearance? | Only for pre-shipment estimates | Yes — the required document |
| Tax implications | None (no VAT/GST liability) | Full tax obligation |
| Can change after issue? | Yes (it's preliminary) | No (corrections need credit notes) |
The critical distinction: a proforma invoice creates no accounting entry. It is not an accounts receivable item for you or an accounts payable item for the client. Until you issue the commercial invoice, no money is owed.
When to Use a Proforma
Four common scenarios where a proforma makes sense:
International trade with prepayment. You're shipping goods to a buyer in another country. They need the proforma to arrange payment (wire transfer, letter of credit) before you ship. Once payment is confirmed, you ship the goods and issue the commercial invoice.
Client needs internal approval. A marketing agency quotes a project at $28,000. The client's procurement team needs a document with line items, quantities, and totals to get budget approval. A proforma gives them that without creating an obligation.
Customs pre-clearance. An importer needs to estimate duties and taxes before goods arrive. The proforma provides the necessary details (item descriptions, HS codes, declared values) for customs to assess duties in advance.
Price confirmation before commitment. The proforma locks in a price for a defined period (typically 30-90 days). If the buyer agrees, you convert it to a commercial invoice. If they don't, no harm done — the proforma expires.
Converting a Proforma to a Commercial Invoice
Once the client accepts and you deliver, you issue a commercial invoice. The commercial invoice should reference the original proforma number ("Per Proforma PI-2026-014") so the client's AP team can match the two documents.
The final amounts may differ from the proforma — exchange rates shift, quantities change, additional charges appear. That's expected. The proforma was an estimate; the commercial invoice is the truth. If the differences are significant, flag them in the email: "Note: the final total differs from the proforma due to the additional 50 units ordered on June 12."
Proforma Invoices and Tax
A proforma invoice has no tax implications. You do not charge VAT or GST on a proforma, you do not report it on your VAT return, and the client cannot claim input tax credit from it. The tax obligation arises only when you issue the commercial invoice.
This is one of the most common mistakes in international trade: issuing a proforma with VAT, leading the buyer to believe they've received a tax invoice. If your proforma includes estimated tax amounts (which can be useful for the buyer's budgeting), label them clearly as estimates: "Estimated VAT (for budgeting only): £2,400."
For VAT specifics, see our UK VAT invoices guide.
Mistakes That Cause Real Problems
- Not labelling the proforma. An unlabelled proforma gets processed as a commercial invoice. The client pays an estimate, then you have to issue a credit note and re-invoice when the real numbers differ.
- Using proformas for customs clearance on actual shipments. Customs authorities require a commercial invoice for clearance. A proforma may be accepted for advance duty estimation, but the shipment will be held until a commercial invoice is presented.
- Recording proforma revenue in your books. A proforma is not revenue. Do not book it. Your accountant (and HMRC or the IRS) will not be impressed.
- Issuing proformas with no expiry date. Prices change. Include a validity period: "This proforma is valid for 30 days from the date of issue."
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