What is the Peppol Message Level Status (MLS)?
The MLS is a standardised status message used within the Peppol eDelivery network, allowing service providers to communicate the outcome of processing and delivering business documents.
The Peppol Message Level Status (MLS) is a standardised status message used within the Peppol eDelivery network. It allows the service provider that receives a business document (C3) to inform the sending service provider (C2) about the outcome of processing and delivering that document. The MLS message is based on the earlier Message Level Response (MLR) specification but extends it to support reporting between Peppol service providers.
Purpose and Use Cases
An MLS message informs the sender (C2) of one of the following situations:
1Message rejected
The business document did not meet conformance rules or could not be delivered to the final recipient (C4).
2Delivery to C4 failed
C3 was unable to forward the message to C4 (e.g., due to technical issues).
3Delivery to C4 succeeded with confirmation
C3 received a verifiable acknowledgement from C4 that the message was accepted.
4Delivery to C4 performed (without confirmation)
The message was forwarded to C4, but C3 has no confirmation of receipt (e.g., delivery via email or postal service).
Important: C3 must not send more than one MLS message per business document, and MLS messages are always sent from C3 to C2 (never in response to another MLS or MLR).
Parties and Roles
MLS uses the Peppol corner model to identify participants:
С1Document Creator
The business entity creating the document (e.g., invoice).
С2Sending Provider
The service provider sending the document and receiving the MLS.
С3Receiving Provider
The service provider receiving the document and creating the MLS.
С4Final Recipient
The final recipient processing the document.
MLS messages enable C2 to monitor whether C3 successfully validated and forwarded the document to C4. This is particularly useful when participants use different service providers or access points.
MLS Process Overview
The MLS process follows a defined sequence:
1Receive documentC3 receives a business document and its message envelope from C2.
2Determine conditionsC3 reads the message envelope (SBDH) to decide whether an MLS should be sent and to which participant ID (C2 or an alternative).
3Validate and forwardC3 performs validations (schema, business rules, etc.) and forwards the document to C4.
3Decide MLS responseBased on validation results and SBDH settings, C3 determines whether to send an MLS and with which response code.
MLS Response Decision Logic:
If validation is successful and SBDH requests MLS only on errors → no MLS sent
If validation is successful and SBDH requests MLS for all outcomes → positive MLS (AP or AB)
If validation fails → negative MLS (RE) with details of the failure
MLS Delivery Preferences (SBDH Extension)
C2 can indicate delivery preferences through optional SBDH fields:
MLS_TO
Specifies an alternative participant identifier to receive the MLS message (useful when C2 operates multiple access points). If the value is invalid, the MLS must be sent to the default C2 service provider ID.
MLS_TYPE
Defines when MLS messages should be sent:
FAILURE_ONLY – send MLS only for rejected messages (RE)
ALWAYS_SEND – send MLS for all outcomes (AP, AB and RE)
If MLS_TYPE is absent or invalid, C3 must use the default policy, which currently requires sending MLS for all response codes.
Response Codes and Meaning
MLS uses a simple three-code system:
| Code | Meaning (overall status) |
|---|---|
| AP | Delivered with confirmation – C3 successfully delivered the message to C4 and received a verifiable acknowledgement. |
| AB | Delivered without confirmation – C3 forwarded the message to C4 but cannot confirm receipt. |
| RE | Rejected / Delivery failed – C3 could not deliver the message due to conformance issues or technical failure. |
When the status is RE, the MLS must include reasons for rejection so that the sender can resolve issues.
Status Reason Codes
If the message is rejected (RE), C3 should include specific status reason codes to indicate why the document was not delivered. The MLS specification defines four reason codes:
An MLS message with rejection (RE) must provide enough detail (issue location, description and classification) for C2 to identify the source of the problem.
MLS Message Structure
The MLS is based on the UBL Application Response format and contains specific business terms (BT) and business groups (BG). Key elements include:
BT-001
References the version of the MLS specification.
BT-002
Indicates the business context of the transaction.
BT-003
Unique ID for the MLS message.
BT-004/005
Date (without time zone) and time (with time zone, preferably UTC) when the MLS was issued.
BT-006 to BT-011
Identify C3 and C2, along with their identification schemes.
BT-010/011
The MLS status (AP, AB or RE) and an optional human-readable description.
Rules and Obligations
The specification sets operational rules for service providers:
Each business document may result in zero or one MLS message.
MLS must be sent as soon as the status is known.
The sender and receiver identifiers in MLS must correspond to C3 and C2, respectively.
The MLS must include the specification and process identifiers, issue date/time, and the original envelope identifier.
MLS messages must not respond to other MLS or MLR messages.
How MLS Differs from MLR
Message Level Response
Validates the document’s structure and is typically sent by the business receiver (C2/C4).
Message Level Status
Focuses on the status of message exchange between service providers (C2 and C3).
MLS informs C2 whether the document was delivered to C4 or rejected due to validation or delivery issues. It provides high-level response codes and reason codes but does not confirm business acceptance by the final recipient; that remains the role of the Business Level Response (BLR).
Summary
The Peppol Message Level Status (MLS) is the mechanism by which a receiving service provider (C3) informs the sending service provider (C2) about the processing and delivery status of a business document within the Peppol network.
It helps ensure that the sender receives timely feedback on whether their document has been delivered or rejected. It uses simple response codes (AP, AB, RE) and detailed reason codes (SV, BV, BW, FD). By adopting MLS, Peppol participants gain transparency and reliability in their inter-provider message exchanges.
