Sending an invoice when your client is not on Peppol

The scenario every supplier eventually hits

You submit a structured invoice through your Access Point — and delivery fails because the recipient cannot be found in the Peppol directory, or no Access Point accepts documents for their participant identifier.

This is a routing problem, not a UBL formatting error. Peppol delivers only to organisations that are registered, discoverable, and reachable. When a Belgian B2B customer is not (yet) on Peppol, technical failure is expected. The harder question is what you may do commercially and legally while the counterparty remains unreachable.

This article addresses domestic Belgian B2B relationships where the structured e-invoicing obligation may apply. It does not describe ways to bypass the mandate.

Why delivery stops at lookup

Before transmission, your Access Point queries the Peppol Service Metadata Publisher (SMP) to determine whether the recipient has a registered participant identifier (in Belgium, commonly the enterprise number under scheme 0208), which Access Point receives their documents, and which profiles they accept (typically Peppol BIS Billing 3.0 for Belgian B2B invoices).

If any step returns no match, delivery cannot proceed:

Before assuming a customer is "off Peppol," perform a deliberate Peppol participant lookup using the correct Belgian enterprise number.

Participant lookup

The directory query an Access Point performs to find where to deliver a structured document. Failure here blocks Peppol transmission regardless of invoice content quality.

When the mandate still applies

Belgium's B2B rules turn on the transaction and the parties, not on whether Peppol delivery succeeded on the first attempt. When both supplier and customer are Belgian VAT-liable businesses within scope, the invoice must be exchanged as a structured electronic document over Peppol — not merely communicated as a PDF.

Non-reachability explains a failed delivery attempt; it does not, by itself, authorise substituting PDF-by-email as the legally sufficient form of exchange when the mandate applies. Edge cases — foreign suppliers, exempt regimes, specific sectors — are defined in legislation. This article focuses on two Belgian VAT-liable businesses where structured exchange is expected.

For the distinction between readable PDF and compliant structured invoice, see PDF vs structured invoice.

PDF by email: interim communication, not a compliance substitute

Emailing a PDF can inform the customer, provide a human-readable copy after successful Peppol delivery, or support internal approval workflows. When the mandate applies, however, a PDF sent by email is generally not sufficient on its own as the form of B2B e-invoice exchange.

The obligation targets structured interoperability, not merely notifying the customer of an amount due. Treating "we emailed the PDF so they have the invoice" as full compliance confuses communication with mandated electronic interchange.

• After successful Peppol delivery — a PDF companion may still be helpful; the structured document remains authoritative
• While Peppol delivery is impossible — a PDF does not cure the compliance gap if both parties are in scope; it may keep commercial dialogue alive, but it is not a substitute for structured exchange

Do not interpret temporary non-registration as permission to abandon structured sending permanently for in-scope B2B invoices.

Practical paths (without invented loopholes)

None of the following replaces the structured obligation where it applies. They reduce friction while working toward compliant exchange.

1. Verify the identifier and retry lookup. Confirm the customer's KBO/BCE enterprise number, correct legal entity, and scheme 0208. Repeat the participant lookup. Many apparent absences are data errors.

2. Ask the customer to register and receive. The durable fix is for the buyer to become Peppol-reachable via Peppol registration in Belgium, publishing receiving capability for BIS Billing invoices. Once directory metadata is live, resubmit the structured invoice. Suppliers cannot register third parties, but may require registration in onboarding checklists — a commercial lever, not a legal workaround.

3. Hold structured submission until reachable (where commercially feasible). Some suppliers pause Peppol submission until lookup succeeds. Legally, delaying structured delivery does not extend statutory issuing deadlines where those exist; balance commercial urgency with compliance planning and advisor input.

4. Document the failure and remediation. Record lookup timestamps, identifiers used, Access Point errors, customer contact about registration, and resubmission dates. This supports audit conversations about good-faith compliance efforts; it is evidence of process, not a guarantee against penalties.

5. Consult qualified advisors on persistent non-compliance. If a material customer indefinitely delays Peppol readiness while remaining in scope, treat it as tax and contract risk, not purely an IT issue.

Access Points typically block outbound transmission when lookup fails, surface directory errors, and allow resend once the customer appears. The compliance principle remains: structured Peppol delivery is the target for in-scope Belgian B2B invoices.

Summary posture