PO number on a Belgian invoice (and how it differs from Peppol Ordering)
A purchase-order number on an invoice is a buyer reference. It is not Peppol Ordering or a BIS Order document. How to show PO / bestelbon on Belgian invoices and when public buyers ask for more.
Updated
- Belgium
A PO number (purchase order, bestelbon, bon de commande) on a Belgian invoice is a buyer reference. It tells accounts payable which order to match. It is not a Peppol document type and it is not “Peppol Ordering.”
If the buyer only needs the number on the invoice, put it in the dedicated PO field (and in structured Peppol data when you send B2B). If they ask you to receive or send orders over Peppol, that is a different profile (BIS Order), not the invoice PO field.
When this applies
- The customer’s AP rejects invoices without a PO
- You see queries like “PO nummer factuur” or “peppol order”
- A public buyer mentions a contract or order reference next to Mercurius
What to put on the invoice
| Field | Role |
|---|---|
| PO / order number | Buyer’s identifier for the purchase |
| Your invoice number | Your gap-free series; never reuse the PO as the invoice number |
| Quote or project ref | Your commercial trail; optional beside the PO |
Legal mentions still apply: Belgian invoice mentions. Numbering stays yours: invoice numbering.
On Peppol BIS Billing, the order reference travels as structured data (order reference / buyer reference), not as a PDF stamp only. AP automation reads the XML.
Invoice PO versus Peppol Ordering
| Concept | What it is | What it is not |
|---|---|---|
| PO on an invoice | A reference string the buyer already issued | A Peppol Order document |
| Peppol Ordering / BIS Order | A separate document type some networks use to send orders | Required for every Belgian B2B invoice |
| Bestelbon / bordereau | Commercial or receiving paperwork | A substitute for a VAT invoice |
Belgium’s 2026 B2B duty is about structured invoices (and credit notes), not about mandating Peppol Ordering for every SME. Do not buy “order software Peppol” unless a specific buyer actually exchanges orders on the network.
Worked example
Atelier Nord invoices commune client C for window repair. The commune issued PO COM-2026-441. The invoice number is F2026-118. The Peppol invoice carries COM-2026-441 as the order reference. That is not a Peppol Order message; it is an invoice that AP can match.
Public buyers and Mercurius
Public entities often require a PO or contract reference before they accept the invoice. Confirm the exact field in their instructions. Routing is still Peppol through your Access Point toward their identity; see Mercurius / B2G.
Common mistakes
- Using the PO as the invoice number (breaks your series)
- Putting the PO only on the PDF while the XML is empty
- Assuming “peppol order” means you must implement BIS Ordering
- Mixing self-billing / bordereau d’achat with a customer PO (different role; see self-billing)
FAQ
What does PO number mean on an invoice?
The buyer’s purchase-order identifier. It is used to match the invoice to an approved order.
Is a Peppol order the same as a PO on the invoice?
No. A PO on the invoice is a reference. Peppol Ordering is another document type (BIS Order), used only when both sides exchange orders on the network.
Must every Belgian invoice have a PO?
No. Only when the buyer requires it. Many SMEs invoice without a PO; large and public buyers often require one.
Where do I put a bestelbon number?
In the purchase-order / order-reference field, not as a replacement invoice number.
Does Mercurius require Peppol Ordering?
Public buyers typically require a structured invoice plus their reference rules. Confirm each entity. Do not assume Ordering is mandatory for all B2G.