What is a Peppol ID, and how do I find a customer's?
Learn what a Peppol participant identifier is, how the Directory and SMP route documents to it, how to look one up, and what to do when a customer isn't listed.
You have agreed to send a customer their invoices over Peppol. Before you can, you need to know where to send them, and on Peppol "where" is not an email address or a company name. It is a participant identifier, the address the whole network routes on.
What a participant identifier actually is
A Peppol ID has two parts: a scheme and a value. The scheme says what kind of number the value is; the value is the number itself. In practice the value is usually a tax or company registration number the business already has: a VAT number or a national enterprise number, and sometimes a GLN, a global location number used more in retail and logistics.
The scheme matters because the same digits can mean different things in different registries. A Belgian company might be addressed by its enterprise number under one scheme or its VAT number under another, and each has its own scheme code. Written out, an identifier is a scheme code followed by the value, and the code tells any access point which register to interpret the number against. That is why "just the VAT number" is sometimes not enough on its own: the scheme has to travel with it.
How the ID turns into a delivery
The SML (Service Metadata Locator) is the network's directory layer, built on DNS. Given a participant identifier, it points to the SMP (Service Metadata Publisher) that holds that participant's details. The SMP record says two things: which access point delivers documents for this participant, and which document types they accept, such as a BIS Billing 3.0 invoice or a credit note.
So when you send, your access point takes the recipient's identifier, uses the SML to find their SMP, and routes the document to the access point named there, provided the recipient accepts that document type. That is the lookup behind the four-corner model described in what is Peppol.
A company can therefore have a VAT number and still not be reachable on Peppol, because reachability depends on that SMP record existing, not on the number existing.
Looking one up
The human-facing tool is the Peppol Directory, a public, searchable index of registered participants. You can search it by company name or by identifier, and if a business appears there with the invoice document type listed, they are reachable.
Search by the exact identifier rather than the name where you can: the descriptive listing is opt-in, so a participant can be reachable on the network without being easy to find by name. And a hit answers "can I reach them", not "will this exact invoice pass every rule". The second depends on the document itself, not on registration. Checking a customer on the Peppol network goes deeper on doing this before you commit to a delivery date.
When the customer isn't listed
Sometimes they are not on the network, and closing that gap is their job: you cannot register a customer as a Peppol participant on their behalf, and no sending tool can either. They register through an access point or service provider, often the same accounting software they already run, after which they have their own identifier and SMP record and become reachable. Until then, you fall back to a PDF by email for that one customer. Ask early, because registration runs on their timeline.
Where this fits if you send from Stripe
If you bill through Stripe, you do not run the SML and SMP lookups yourself. When you start a send in Peppost, it resolves the recipient's identifier against the Peppol Directory and confirms they accept the document, and it does this before any credit is spent, so a customer who is not on the network is reported back without charging you. The sending guide shows where that check sits in the flow, and the FAQ covers what the lookup does and does not promise.