Peppol invoice attachments for construction: keep the evidence usable

Attachments support the invoice; they do not replace its data

A construction invoice may need a progress statement, signed work order, delivery note, measurement sheet or photo report. Peppol can carry attachments, but the structured invoice must still contain the required invoice data. A PDF or spreadsheet cannot be used as a container for totals that are missing from the structured document.

Belgium's official B2B e-invoicing questions address attachments and the relationship between the structured invoice and optional supporting files. The practical rule is simple: make the invoice independently identifiable, then attach only evidence that helps the recipient validate it.

Start from the customer's approval process

Ask what the customer actually needs before the first invoice. A private client, general contractor and public authority may use different references and controls. Record the agreed purchase-order number, project code, contract reference and approval contact on the customer or project record.

For each supporting file, answer:

• which invoice line or billing period it supports;
• who approved the underlying work;
• whether it contains personal or unnecessary information;
• whether the recipient can open the format;
• which version is final;
• whether the same evidence must remain in the project file.

Do not attach an entire site photo archive when a signed progress statement is the agreed evidence.

Use clear names and stable references

Name files for the reader, not for the device that created them. A name such as Project-Orchard-progress-03-approved.pdf is more useful than scan0047.pdf. Put the project and period in the file itself so it remains understandable after download.

Keep invoice line descriptions aligned with the supporting statement. If the invoice says “phase 3”, the attachment should not use a different phase number or an outdated amount. For change orders, reference the accepted change document rather than placing unexplained extra work in a general attachment.

Separate commercial evidence from internal notes

Before sending, remove internal comments, draft calculations, unrelated customer data and photographs that reveal people without a business need. The invoice recipient needs evidence for approval, not the full internal project history.

Maintain your own project record separately. It should contain the approved source, the invoice sent, its attachments and the transmission status. If the customer asks a question six months later, your team should be able to reconstruct why the amount was billed without searching personal mailboxes.

Validate delivery and readability

A successful attachment upload is not proof that the recipient received a usable invoice. Check the delivery status from your provider and keep any returned error. Ask the customer to confirm its required reference when an invoice is routed to the wrong approver; do not keep adding copies of the same document to a new invoice.

If an issued invoice must change, follow the correction process. Do not replace the original attachment silently, because that breaks the link between the evidence the customer reviewed and the amount that was issued.

For the broader delivery process, see the Belgian Peppol practical guide. Review digital invoice archiving to keep the document and its evidence together after delivery. To connect project records with invoicing, explore Enfin.