Peppol BIS Message Level Response (MLR) is a UBL ApplicationResponse used to report whether a received business document has passed message-level validation. It can acknowledge a document or report that it was accepted or rejected at this processing layer.

An MLR is not automatically returned for every successful exchange. Its use depends on the applicable process and implementation.

The principal MLR response codes are:

MLR is distinct from a transport receipt and from a business response. A transport receipt concerns network transmission. A business response, such as Invoice Response or Order Response, records a decision made after the document has entered the recipient’s business process.

OpenPeppol is replacing MLR with Message Level Status (MLS) in the eDelivery layer. The MLS activation window starts on 1 March 2027, MLS becomes mandatory for service providers on 1 April 2027, and MLR is retired on 1 May 2027. Implementations should plan their migration accordingly.

See the official MLR documentation, the official MLR phase-out plan and the article about Peppol Message Level Status.