When a customer portal cannot replace the agreed Peppol channel for a Belgian contractor

A customer portal can collect project documents, approve progress or feed an internal accounts-payable workflow. That does not automatically make it the correct legal delivery channel for a Belgian structured invoice. Treat portal submission and invoice delivery as two separate decisions, then document what the parties have actually agreed.

Start with the transaction, not the customer's interface

Identify the supplier, customer, VAT status and transaction before choosing a channel. For Belgian B2B transactions within the 2026 structured-invoicing obligation, the federal guidance says invoices must in principle be exchanged through Peppol. A client cannot unilaterally require exclusive submission through its own portal unless the supplier expressly agrees. The current position is explained in the Belgian federal B2B e-invoicing FAQ.

Do not assume that every invoice touching a Belgian construction site has the same treatment. Cross-border parties, consumer work and other exceptions need their own scope check. When the classification is unclear, pause and ask the accountant or tax adviser rather than selecting a channel from habit.

Give the portal a precise job

A portal may still be useful for a purchase-order reference, measured quantities, signed progress statement or approval status. State whether uploading there is an administrative copy, a prerequisite for customer processing or an expressly agreed invoice-transfer method. This prevents the site team from believing that an upload completed the statutory delivery step.

Keep evidence of both actions when both are required: the structured invoice exchange and the portal submission. Use the same invoice number and project reference so the customer can match them, but avoid creating a second invoice merely to satisfy the portal layout.

Handle a not-ready customer as an exception

The federal FAQ describes a fallback when a customer is not ready to receive through Peppol. An alternative transfer may be used, with agreement where required and a secure method. Once the customer becomes operational, suppliers do not need to resend old invoices retroactively. Record the failed or unavailable route, the agreed alternative, the recipient, the time and the evidence of delivery.

This exception is not permission to choose ordinary email for convenience. Confirm that it applies to the actual invoice and that the alternative preserves integrity and readability. Professional advice is appropriate when the customer disputes the channel or the transaction is cross-border.

Close the loop before marking the invoice sent

Use a short control: correct legal entity, correct invoice, correct Peppol recipient, correct portal case, required attachments and proof for each channel. Assign an owner if any item is uncertain. A project manager may know the purchase order, while finance confirms the invoice route.

Enfin can keep customer, project and invoice context together. It should not be presented as overriding the customer's agreement or deciding legal scope automatically.

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