Peppol MLS (short for Message Level Status) is a technical status message that your buyer's service provider (called C3 in Peppol's four-corner model, where two providers sit between you and your trading partner) sends back to the provider that sent your e-invoice (C2), reporting exactly what happened to that document. It is not a business reply from the buyer. Under Peppol's MLS specification v1.1.0, MLS exists so two providers can check each other's reliability, not so the buyer can confirm whether they actually received, approved or paid the invoice. The global rollout of MLS has begun 1 July 2026, but providers won't be required to actively send MLS messages until 31 March 2027. Until that date, seeing no positive status at all is completely normal; it's not a sign anything's wrong.

Does AP mean the buyer received and approved the invoice?

Well. AP means your buyer's provider holds verifiable proof that the document reached the final recipient (C4) for processing. That proof might be, say, an acknowledgment returned through a software API. As per the specification, AP can't be used when the document is delivered to C4 by email; in that case the only positive status available is AB. So AP is solid technical evidence that the invoice reached the doorstep of the buyer's system, but it isn't evidence that a bookkeeper actually looked at it, let alone started paying it.

What do RE, AP and AB actually mean?

RE means the document never reached C4's processing at all. The most common causes are a schema or business-rule error, a virus, a broken attachment, a file that's too large, or a persistent delivery failure. AP means verifiable confirmation that the document reached C4. AB means C3 forwarded the document towards C4 but can't confirm it actually arrived. That's what happens with email delivery, file transfer, or a local drop folder the recipient only reads from later. If C3 hits a temporary glitch, it uses AB and keeps trying; that's not the same as a permanent RE rejection.

Why does a correctly sent invoice sometimes show no positive status?

The most common reason is not a failure. It's a default setting. The specification sets the default mode to FAILURE_ONLY: unless your outgoing envelope carries the flag MLS_TYPE=ALWAYS_SEND, your buyer's provider will only send back a negative RE response if something goes wrong; it won't bother sending a positive AP or AB at all. So a missing status doesn't mean the invoice disappeared. It usually just means nobody asked for positive confirmation in the first place.

What to ask your e-invoicing provider before 2027

Providers have production-ready receiving capability by 28 February 2027, ahead of the 31 March 2027 deadline when active sending becomes mandatory. Ask your software or operator three things: whether they already support receiving MLS, whether AP and AB statuses will actually show up in your interface, and whether, for smaller documents, they meet the speed set out in Peppol's Network Policy, which requires 99.5% of MLS messages to arrive within 20–25 minutes. And keep one thing straight: MLS doesn't replace the agreement with your trading partner on invoice format and acceptance terms required under Estonia's Accounting Act. Real approval still comes from the buyer, never from the Peppol network itself.

FAQ

Does AP mean that the buyer received and approved the invoice?

No. AP is a technical confirmation that the document has reached the final recipient (C4) for processing, not a commercial approval of the buyer. AP does not prove that the accountant saw the invoice or started paying.

What do the Peppol MLS statuses RE, AP and AB mean?

RE – The document did not reach C4 for processing (schema error, virus, broken attachment, too large file). AP – Verifiable confirmation that the document reached C4. AB – C3 forwarded the document, but cannot confirm its arrival (e.g. by email).

Why does a correctly sent invoice not have a positive status?

The most common reason is the default setting FAILURE_ONLY - if the envelope does not have MLS_TYPE=ALWAYS_SEND, the service provider will only send back a negative RE, not a positive AP or AB. No one has requested a positive confirmation.

When will Peppol become mandatory for MLS service providers?

The service provider must have reception capability in production no later than February 28, 2027. Active MLS sending will become mandatory on March 31, 2027.