As of 1 January 2026, Belgium requires all VAT-registered businesses to issue and receive structured electronic invoices for domestic B2B transactions, using formats compliant with EN 16931 (Peppol BIS 3.0 is the recommended standard and network). Traditional PDF invoices are no longer accepted for in-scope transactions.

This means many self-employed and small business users in Belgium (and increasingly across the EU, as similar mandates roll out elsewhere) now legally need to send and receive invoices via the Peppol network rather than as email attachments.

Could Proton consider:

Native integration with the Peppol network (as an Access Point, or via partnership with an existing certified Access Point), allowing Proton Business users to send/receive Peppol-compliant e-invoices directly.
At minimum, documentation or guidance on how Proton Mail/Business fits into a compliant invoicing workflow now that plain PDF-by-email is no longer sufficient for Belgian B2B invoices.

This is becoming a hard legal requirement, not a nice-to-have, for a growing share of your self-employed and small-business customer base in Belgium. Support here would be a meaningful differentiator, especially as similar EU-wide requirements are expected from 2030 onward.