The short answer
A pro forma invoice is a priced preview of an invoice: it shows what the customer will pay, but it is not an invoice for VAT. It makes no VAT chargeable, does not belong in your sales invoice book and gives the customer no right to deduct VAT. An advance invoice (also called a deposit or prepayment invoice) is a real invoice. VAT on an advance becomes chargeable when you receive the payment, and the invoice is due by the 15th day of the following month. The final invoice states the full price, deducts the advance and charges VAT only on the balance. Since 1 January 2026, an advance invoice between two Belgian VAT-registered businesses is a structured e-invoice sent over Peppol; a pro forma falls outside that obligation.
The rules below come from Royal Decree No. 1 on VAT (on Justel), the EU VAT Directive, FPS Finance's invoicing page, the e-invoicing FAQ on einvoice.belgium.be and the Peppol BIS Billing 3.0 documentation, read on 1 October 2026. This is general information, not tax advice.
Quote, pro forma, advance invoice, invoice: four different documents
Document | What it does | Invoice for VAT? | VAT effect | Between Belgian VAT payers since 2026 |
|---|---|---|---|---|
Quote | Offers a price and terms; the customer's acceptance turns it into an agreement | No | None | PDF or email, outside the e-invoicing obligation |
Pro forma invoice | Shows what a future invoice will look like, often so the customer can approve or prepay | No | None; the customer cannot deduct anything from it | PDF or email, outside the e-invoicing obligation |
Advance invoice | Invoices a payment received before the goods or services are supplied | Yes | VAT chargeable on the amount received, when it is received | Structured e-invoice over Peppol |
Final invoice | Invoices the supply and deducts any advances already invoiced | Yes | VAT on the balance only | Structured e-invoice over Peppol |
For the first step, see how to write a B2B quote.
The pro forma invoice: what it is for
No Belgian VAT text defines a pro forma invoice. Its status follows from what the rules do define: an invoice is issued for a supply, or for a payment received before a supply. FPS Finance lists exactly those cases under the invoicing obligation. A pro forma comes before either, so nothing is chargeable yet and there is nothing to invoice.
Businesses use a pro forma when:
the customer needs a formal document to approve a purchase or release a budget;
you want payment before you deliver and the customer will not pay from a quote.
Three practical rules keep it clean. Write "pro forma" prominently, so nobody books it as a purchase invoice. Do not give it a number from your invoice series: Royal Decree No. 1 requires invoices to carry a sequential number under which they are entered in your outgoing invoice book, and a pro forma does not belong there. And do not expect the customer to deduct VAT from it: the einvoice.belgium.be FAQ states that deducting VAT requires a regular invoice, citing article 3, §1, 1° of Royal Decree No. 3.
The advance invoice: when VAT becomes due
The EU VAT Directive sets the rule for payments on account: VAT becomes chargeable on receipt of the payment and on the amount received (article 65). It also requires an invoice for any payment on account received from another business (article 220). In Belgium, Royal Decree No. 1 sets the deadline: when VAT becomes chargeable on all or part of the price under article 17, §1, third paragraph of the VAT Code, the invoice must be issued no later than the 15th day of the month after the one in which that happens. That wording has applied since 1 January 2016.
In practice: if a customer pays a deposit on 20 October, the advance invoice is due by 15 November, and the VAT on the deposit belongs to the period in which you received it. Many businesses therefore ask for the deposit with a pro forma and issue the advance invoice once the money arrives.
What must be on an advance invoice
An advance invoice carries the same mentions as any invoice under article 5 of Royal Decree No. 1, including:
the issue date and a sequential invoice number;
your name, address and VAT number, and the customer's name, address and VAT number;
the date you received the advance, if it is known and differs from the issue date;
a description of the goods or services the advance relates to;
the taxable amount per VAT rate, the rate and the total VAT;
where relevant, the reverse charge mention or the exemption ground.
Add a reference to the quote or order, such as "30% advance on order 2026/118". It is not a legal mention, but it helps both accounting teams.
How the final invoice deducts the advance
Royal Decree No. 1 covers this directly: when several invoices are issued for the same transaction, the later one must refer to the earlier ones, and it may not charge the customer VAT that was already charged. The final invoice therefore shows the full price, subtracts the advance with a reference to the advance invoice number, and calculates VAT on what is left.
An illustrative example: a 10,000 euro job, VAT at 21%, 30% advance.
Line | Advance invoice | Final invoice |
|---|---|---|
Price of the job excl. VAT | 3,000 euros (30% advance) | 10,000 euros |
Advance already invoiced | - | minus 3,000 euros (ref. advance invoice 2026/0142) |
Taxable amount | 3,000 euros | 7,000 euros |
VAT at 21% | 630 euros | 1,470 euros |
Amount to pay | 3,630 euros | 8,470 euros |
Together the two invoices charge 2,100 euros of VAT, exactly 21% of 10,000 euros. If the order is cancelled after the deposit, you do not delete the advance invoice: you correct it with a credit note that refers to it. How credit notes work in Belgium covers the mentions and the Peppol side.
Pro forma and advance invoices on Peppol
Since 1 January 2026, structured e-invoicing is compulsory for transactions between Belgian businesses liable to VAT, and the einvoice.belgium.be FAQ is explicit that the structured e-invoice is the only legally required invoice; a PDF copy is optional. An advance invoice is an invoice, so between two Belgian VAT payers it goes over Peppol. The Peppol BIS Billing 3.0 code list has a dedicated type for it: code 386, "Prepayment invoice". On the final invoice, the format has a "paid amount" field (business term BT-113) that lowers the amount due. How your software nets out the VAT already invoiced differs per package, so check that the VAT total on the final invoice covers only the balance.
A pro forma is different. The FAQ on einvoice.belgium.be does not mention pro forma invoices, and the obligation covers invoices and the credit or debit notes that correct them. A pro forma is neither, and the Peppol BIS invoice type list has no pro forma code. Send it as a PDF. Do not push it through Peppol as an invoice: the customer's software would book it as a purchase invoice.
On Peppol, the customer's enterprise number is its address, so a wrong number sends the advance invoice to another company. Peppol in Belgium explained covers the obligation in full, and how to check if a company is on Peppol shows the lookup. Bizzy shows the enterprise number, VAT number and legal form from the KBO for Belgian companies and can write them into HubSpot, Salesforce, Pipedrive, Microsoft Dynamics 365, Teamleader Focus or Odoo. Whether the customer is subject to VAT at all decides whether Peppol applies; see who is liable for VAT in Belgium.
Which document to send when
Situation | Send |
|---|---|
The customer wants a price before deciding | Quote |
The customer needs a formal document to approve or pay upfront | Pro forma invoice, by PDF |
You have received a deposit | Advance invoice, by the 15th of the following month, over Peppol if both are Belgian VAT payers |
The job is done or the goods are delivered | Final invoice with the advance deducted |
The order is cancelled after a deposit | Credit note referring to the advance invoice |
Frequently asked questions
Is a pro forma invoice a real invoice in Belgium? No. It is a preview of a future invoice. It makes no VAT chargeable and gives the customer no right to deduct VAT.
When does VAT become due on a deposit? When you receive the payment, on the amount received. The advance invoice must be issued by the 15th day of the following month.
Do I send a pro forma via Peppol? No. The e-invoicing obligation covers invoices and credit or debit notes, and Peppol BIS has no pro forma document type. Send it as a PDF. Advance invoices between Belgian VAT payers do go over Peppol.
How do I deduct a deposit on the final invoice? Show the full price, subtract the advance with a reference to the advance invoice, and charge VAT only on the balance.
Photo: the collegiate church of Sainte-Gertrude in Nivelles, Cochon d'inde noir, CC0, via Wikimedia Commons