How do I send an e-invoice to a public authority (Mercurius)?

You had to send e-invoices to public authorities long before the general obligation between businesses. Public contracts published after 1 March 2024 are covered; the royal decree of 9 March 2022 sets out the rules.

How do I know whether my customer is a public authority?

Look up your customer in the Crossroads Bank for Enterprises (KBO). If the section “Hoedanigheden” (Capacities) shows the entry “Aanbestedende overheid - Sinds [datum]” (Contracting authority - Since [date]), the obligation for public authorities applies to them.

You can see whether your customer is on Peppol with the check below:

With software

All European contracting authorities must be able to receive structured e-invoices that follow the European standard. If you have invoicing software that is connected to Peppol, you simply send the invoice just as you would to any other customer.

Without software: the Mercurius portal

If you don’t have suitable software yet, you can enter your invoices and credit notes by hand in the government’s Mercurius portal in the meantime. Mercurius also helps you track the receipt and processing of your invoices across all your public authority customers.

The government does strongly recommend getting an e-invoicing tool or upgrading your current one: since 1 January 2026, you need one anyway for your invoices to other businesses. Read How do I register my business on Peppol?.