Proforma Invoice: What It Is & When to Use One

A proforma invoice is a preliminary document sent before work is completed or goods are delivered. It looks like an invoice and contains similar information, but it's not a demand for payment. Instead, it's an estimate or quote presented in invoice format — a preview of what the final invoice will look like.

The term "proforma" comes from Latin, meaning "for the sake of form." In practice, it serves as a formal declaration of intent: here's what I'm going to charge you, for what, and on what terms. The client can review it, get internal approval, and prepare the payment — all before the actual work begins.

Critically, a proforma invoice has no legal standing as an invoice. It doesn't create an obligation to pay, it can't be used to claim input VAT, and it shouldn't appear in your sales records as issued income. It's a pre-transaction document, not a record of a completed sale.

Once the goods are delivered or services completed, you replace the proforma with a proper tax invoice. The final invoice may match the proforma exactly, or it may differ if the scope changed during the project. The proforma is simply superseded — it doesn't need to be voided or cancelled.

The difference between a proforma invoice and a tax invoice is fundamental, even though they often look identical on paper:

• Tax invoice — A legal document issued after goods or services are delivered. It demands payment, appears in your accounting records as revenue, and (if you're VAT-registered) triggers VAT obligations. Your client can use it to claim input VAT.
• Proforma invoice — A preliminary document issued before delivery. It does not demand payment, does not appear in your sales ledger, and carries no VAT implications. It's essentially a formalised quote.

To avoid confusion, clearly mark any proforma invoice with the words "PROFORMA INVOICE" at the top — never just "Invoice". If a proforma is mistaken for a real invoice, it could cause accounting errors for both you and your client.

Another key difference: proforma invoices do not require a sequential invoice number from your main numbering system. You can number them separately (e.g., PI-001, PI-002) or use a project reference instead. Your real invoice numbers should only be assigned to actual tax invoices — the documents that represent real transactions.

If you need a formal price commitment without invoicing conventions, a proposal, quote, or estimate may be more appropriate. A proforma invoice is best when the client specifically needs the information in invoice format — for example, to raise a purchase order or arrange a bank transfer in advance.

Proforma invoices are useful in several specific situations:

New client onboarding. When working with a new client — especially a larger company — they may need a proforma invoice to raise a purchase order or get internal budget approval before you start work. The proforma gives their finance team the exact details they need in the format they expect.

Deposits and advance payments. If you require a deposit before starting work, a proforma invoice for the deposit amount formalises the request. Once the deposit is paid, you issue a proper tax invoice for the deposit. This is particularly common for project-based work where you want 30-50% upfront.

International transactions. In cross-border trade, proforma invoices are often required for customs declarations, import licences, and international banking. They declare the expected value of goods being shipped, allowing customs authorities to calculate duties before the goods arrive.

Client budget planning. Some clients request proforma invoices so they can allocate budget for upcoming work. The proforma acts as a commitment of what the final cost will be, allowing the client to reserve the funds internally.

Government and public sector work. Many public sector organisations require a proforma invoice to process a purchase order before any work begins. Without it, they literally cannot raise the PO that authorises your work and eventual payment.

If your client simply asks "can you send me an invoice for this?" before the work is done, they often mean a proforma. Clarify with them, then clearly label the document accordingly.

A proforma invoice should contain the same information as a regular invoice, with a few important additions and differences:

• "PROFORMA INVOICE" heading — Make this prominent and unmistakable. It must be clear that this is not a demand for payment.
• Your business details — Name, address, contact information, and company registration number if applicable
• Client details — Their name, company, and address
• Proforma reference number — Use a separate numbering sequence (e.g., PI-001) rather than your main invoice numbers
• Date and validity period — Include the date of issue and how long the quoted prices are valid (e.g., "Valid for 30 days")
• Detailed line items — Descriptions, quantities, unit prices, and line totals, exactly as they would appear on the final invoice
• Subtotal, VAT (if applicable), and total — Show the full cost breakdown so the client knows what to expect
• Payment terms — State the terms that will apply to the eventual tax invoice
• Notes — Include any relevant conditions, such as "This is not a tax invoice. A VAT invoice will be issued upon completion of work."

The goal is to make the proforma as close to the final invoice as possible, so there are no surprises when the real invoice arrives. If the scope or pricing changes between the proforma and the final delivery, issue an updated proforma or simply explain the differences when you send the tax invoice.

In the UK, a proforma invoice has no legal standing as a tax document. Here's what that means in practice:

VAT treatment. A proforma invoice does not trigger a VAT liability. You should not include it in your VAT return, and your client cannot use it to reclaim input VAT. Only the final tax invoice — issued after delivery — counts for VAT purposes. If you're VAT-registered, make sure your proforma is clearly labelled so neither party's accountant accidentally includes it in VAT calculations.

Accounting records. Do not record a proforma invoice as revenue in your accounts. It's a pre-sale document. Recording it as income would overstate your revenue and could cause problems with HMRC. Keep proforma invoices filed separately from your issued tax invoices.

Legal enforceability. A proforma invoice is not a contract. It doesn't legally bind either party — the client isn't obligated to pay it, and you're not obligated to deliver at the quoted price (unless there's a separate contract in place). If you need legal enforceability, use a contract or formal agreement alongside the proforma.

Converting to a tax invoice. When the work is complete and you're ready to bill, issue a proper tax invoice with a number from your main sequence. You can reference the proforma: "As per proforma PI-003 dated [date]." The proforma is then superseded — you don't need to cancel or void it.

The bottom line: proforma invoices are useful commercial documents, but they're not invoices in the legal or tax sense. Treat them as formalised quotes and you won't go wrong.