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Are you exchanging electronic documents with your business partners through the Peppol network using SAP Document and Reporting Compliance, cloud edition? If so, you have probably come across terms such as Transport Acknowledgement (Acks), Message Level Response (MLR) or Business Level Response (BLR). And you might already know that all three refer to types of messages that are exchanged in Peppol's 4-corner model. However, it might not be completely clear to you when and why each of these message types is sent, what information they convey, or how they look in the eDocument Cockpit or the Manage Electronic Documents app of your SAP S/4HANA, SAP ERP, or SAP S/4HANA Cloud system. With this blog, we would like to bring some clarity into these questions.
Additionally, we will talk about message types developed by SAP to update the status of the electronic document in the SAP business system. Even though, these message types are not part of the OpenPeppol specification, we are mentioning them for the sake of completeness of all message types in the process of sending an electronic document using SAP Document and Reporting Compliance, cloud edition.
Message Types
In general, you can think of the message types as a multi-stage check to ensure the reliable transmission of an electronic document over the Peppol network. Each message type confirms the status of a different stage in the transmission process.
Let's walk through the different message types using a concrete example. In the example, your business system is SAP S/4HANA Cloud, so the sender (corner 1) is represented by the Manage Electronic Documents app, and you are using SAP Document and Reporting Compliance, cloud edition (corner 2) to send electronic documents through the Peppol network to your business partners.
Example: Message types exchanged in Peppol’s 4-corner model when you send electronic documents
The starting point in the Peppol 4-corner model is the first corner where you, as the sender, submit an invoice in the Manage Electronic Documents app to your business partner. The document is then sent to the sender access point (corner 2) which is your SAP Document and Reporting Compliance, cloud edition - this is the corner where the first message type is created.
Message type: Confirmation from SAP Document and Reporting Compliance, Cloud Edition
This message type is not part of the message types defined by OpenPeppol but was developed by SAP as an additional layer to ensure that your document has securely and correctly reached the sender access point.
In the cloud edition (your sender access point), two things are checked:
1. Has the document arrived at the sender access point?
- If yes, the cloud edition sends a message to your business system and the status in your Manage Electronic Documents app changes to Received by Sender Access Point.
- If no, the cloud edition does not send a message to your business system and the status in your Manage Electronic Documents app stays in Sending Requested.
2. Does the document pass the validation checks? The validation checks involve comparing the document with the Schematron rules stored in the sender access point and making sure the receiving participant in the Peppol network can be identified by the sender access point. If the document doesn’t pass the validation checks, the cloud edition sends a message to your business system and the status in the app changes to Error at Sender Access Point.
To resolve errors that appear at this stage you can check the Troubleshooting guide or the SAP Help Portal.
Message type: Transport Acknowledgement (Acks)
When your document has been sent to the sender access point and has successfully passed validation there, the sender access point (corner 2) forwards the document to the receiver access point (corner 3). The receiver access point creates the next message type – the transport acknowledgement.
The forwarding of the document to the receiver access point as well as the transport acknowledgement is accomplished using the Applicability Statement 4 (AS4) messaging protocol. It is based on web services standards and is commonly used for the secure and reliable exchange of documents such as purchase orders, invoices, and shipping notices.
The message transfer in AS4 involves the following steps:
- Message Creation: The sender access point creates the message to be sent, which typically includes the actual document and any necessary metadata.
- Message Packaging: The message is then packaged according to the AS4 standard, which defines the structure and format of the message. The packaging includes adding headers, security information, and other necessary elements.
- Adding Digital Signature: After the message has been packaged, a digital signature is generated using the sender's private key. This digital signature is added to the message. This not only validates the sender’s identity, but also ensures the integrity of the message during transmission as it can be used to detect any changes made to the message after it has been signed.
- Message Transmission: The packaged message along with the digital signature is transmitted over the Peppol network, using HTTP protocols.
- Message Receipt: Once the receiver access point receives the message, it verifies the digital signature using the sender’s public key. If the verification is successful, it indicates that the message was not tampered with during transmission and was indeed sent by the claimed sender.
- Transport Acknowledgment: After the successful verification of the digital signature, the receiver access point sends back an acknowledgment to the sender access point to confirm the successful receipt of the message.
Once the transport acknowledgement reaches the cloud edition (corner 2), the cloud edition sends a message to your business system (corner 1) that triggers the status update in the Manage Electronic Documents app to Acknowledged by Receiver Access Point.
In the case of an unsuccessful message transfer using the AS4 protocol, such as a header error in the message, the receiver access point can’t send a transport acknowledgment to the sender access point. However, it's important to note that the cloud edition (corner 2) still ensures transparency in this scenario by sending a message to your business system, triggering a status change in the Manage Electronic Documents app to Rejected by Receiver Access Point.
Overall, AS4 ensures secure and reliable message transfer in B2B communication, and the use of digital signatures adds an additional layer of security and trust to the process.
Message type: Message Level Response (MLR)
The receiver access point performs another round of validations on the invoice, particularly focusing on the Schematron rules. Since there are multiple versions of these rules, the sender access point and the receiver access point might be checking against different versions. Hence, a document might pass the validation at the sender access point and fail at the receiver access point.
The message that can be sent by the receiver access point to inform about the validation status is referred to as Message Level Response (MLR). Let’s have a look at the scenarios:
- You have enabled receiving MLR in the Configure Participants app of the cloud edition.
- If the receiver access point supports the sending of MLR, you receive an MLR message with the information whether the receiver access point accepted or rejected the electronic document after the validation. In your Manage Electronic Documents app you’ll therefore see either the status Accepted by Rec. Acc. Point or Valid. Error at Rec. Acc Point.
- If the receiver access point doesn’t support the sending of MLR, you won’t receive an MLR message. In your Manage Electronic Documents app you’ll therefore see the status Acknowl. by Rec. Acc. Point.
- You haven’t enabled receiving MLR in the Configure Participants app of the cloud edition: Then of course you won’t receive an MLR message and in your Manage Electronic Documents app you’ll see the status Acknowl. by Rec. Acc. Point.
MLR messages contribute to the overall robustness, reliability, and traceability of the Peppol network by enabling businesses to ensure that their business messages have been successfully received and processed, and quickly identify and rectify issues.
For more information about the Message Level Response, check out this page in the help portal: Message Level Response
Message type: Business Level Response (BLR)
Finally, the receiver access point forwards the document to the receiver (corner 4). The receiver system, or the users themselves, can then decide whether they wish to communicate something to the sender. This means, BLR messages are optional and may not be sent by the receiver. This message, originating from the receiver, is called a Business Level Response (BLR), as it provides information on the business decision relating to the business document.
Unlike the MLR, which is an automated technical confirmation of the message receipt and processing, the BLR concerns the actual outcome of the business message.
The BLR message is forwarded through all the corners and depending on the BLR the statuses in the Manage Electronic Documents app can change. For example, if the original document is an invoice, the following statuses can appear:
- In Process by Receiver
- Under Query by Receiver
- Conditionally Accepted by Rec.
- Acknowledged by Receiver
- Accepted by Receiver
- Rejected by Receiver
- Partially Paid by Receiver
- Paid by Receiver
For more information about the Business Level Response, check out this page in the help portal: Business Level Response.
How to check all those messages in your system
You can trace all the messages from the beginning to the end of the exchange process in the Manage Electronic Documents app in your SAP S/4HANA Cloud system or in the eDocument Cockpit in your SAP ERP, SAP S/4HANA system.
In the Manage Electronic Documents app, expand the Details of the electronic document.
In the Attachments section, you can choose Preview to view the messages.
In the eDocument Cockpit, navigate to Goto > History, to access the History of the electronic document.
In the EDocument History view, you can scroll to the right until you see the File Name column. By double-clicking on the files you can view the messages.
How to enable the message types
If you are in the latest support package for your release, all message types that we previously described are already enabled in your business system for all countries supported by SAP that exchange invoices over the Peppol network. For the sending of Business Level Response, we currently only support Invoice Responses with Accepted and Rejected status, with the exception of Singapore, where we also support Invoice Responses with Acknowledged status.
In the cloud edition however, you must activate the Message Types in the Configure Participants app. This can be done while setting up a participant for your company, by selecting the various message types under the Additional Document Types field. See Registering Your Company to Send Electronic Documents in the Peppol Network.
If you are not in the latest support package of your SAP S/4HANA or SAP ERP system, you can manually implement the following SAP Note: 2783795 - Electronic Document Processing for Peppol Countries/Regions: Implementation Overview.
Further information
For further information about the message types that are part of the OpenPeppol specification, check this page: BIS Message Level Response 3.0
For detailed information about the subcategory Invoice Response of the Business Level Response type, check this page: BIS Invoice Response 3.2
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