Peppol references for Belgian public-contract construction invoices

A correct amount can still fail routing

Public-sector invoice processing depends on references that connect the structured invoice to the authority's order, contract or case. Put the required reference in the designated structured Peppol field; do not rely on text that appears only in a printable attachment. Treat reference preparation as a control step before transmission, not as a note added after rejection.

Start with the purchase order, contract documents and invoicing instructions for the specific authority. Record the buyer's legal identity and electronic address, the required order or case reference, contract number, project or lot and any named contact. Do not copy a reference from the previous invoice without checking that it covers the current progress period.

Map each value to the structured field

Keep a clear distinction between invoice number, buyer reference, purchase-order reference, contract reference and project reference. Your software should show both the business label and the structured field that will be sent. If one invoice covers several orders, follow the buyer's instructions and the supported Peppol structure rather than combining numbers in an unreadable text field.

The Belgian e-invoicing FAQ explains that structured invoices and related processes rely on the agreed network and format. Specific public bodies can impose documented routing references for their own workflow. Those local instructions are not universal rules for every Belgian authority.

Validate before sending

Check the buyer endpoint, currency, totals, VAT treatment, period, attachments and all required references. Compare spelling, spaces and punctuation when the receiver expects an exact value. Ask the project owner to confirm the progress statement or acceptance evidence before the finance user sends the invoice.

Store the submitted structured document, readable rendering, attachments and transmission identifier together. A successful network delivery only confirms transport. Track acceptance, rejection and payment status separately. When a rejection arrives, preserve the original attempt, correct the identified field and send a controlled new version according to the applicable process.

Keep project and finance records aligned

Link the invoice to the same contract, lot and milestone used by the project team. That lets staff explain which work the authority is being asked to pay. It also prevents a technically valid invoice from being assigned to the wrong project internally.

Enfin can structure invoice and project context, but the contracting authority's current instructions remain decisive. Review the Belgian Peppol guide, Peppol invoice attachments and progress invoicing from planning.

Sources: Belgian e-invoicing B2G FAQ and specific e-invoicing questions, checked 1 August 2026.