Registered office clauseThe articles name the region of the registered office. The language of official documents depends on that region, among other things.
Being listed in the Peppol Directory is voluntary, so the company can still receive invoices via Peppol.
Invoicing without a Peppol listing
Try sending from your invoicing software. If that fails, ask the customer whether they already receive via Peppol.
The obligation holds between Belgian VAT-registered businesses. Checked does not know whether this customer is VAT-registered. If it is and is not ready yet, you may send the invoice another way, for example as a PDF. To send it electronically you then need its agreement on a secure channel. The invoice remains valid, and it is then the customer, not you, who risks a penalty. FPS Finance
Follow this company and you will hear the next morning if it appears in the Peppol register.