UAE E-Invoicing MLS Status Codes: What AB, AP & RE Mean and How to Handle Rejections

MLS (Message Level Status) helps businesses understand what happened to an e-invoice after it entered the Peppol network. In the UAE's Peppol-based e-invoicing framework, MLS messages communicate whether a document was delivered, forwarded, or rejected during processing.

Key Takeaways

• MLS stands for Message Level Status and operates within the Peppol network.
• MLS messages are exchanged between service providers, specifically from the recipient ASP to the sender ASP.
• The three MLS response codes are AB (Accepted without confirmation), AP (Accepted with confirmation), and RE (Rejected).
• AP indicates successful delivery with confirmation.
• AB indicates forwarding without delivery confirmation.
• RE indicates that the document was not delivered to the final recipient for business processing.
• Each business document receives zero or one MLS message.

What Is Message Level Status (MLS) in UAE E-Invoicing?

The UAE e-invoicing framework is based on the Peppol 5-corner model. Within this framework, MLS provides visibility into how an electronic document is processed and delivered after it is transmitted through Accredited Service Providers (ASPs).

Message Level Status (MLS) is an OpenPeppol specification used by service providers to communicate the processing outcome of a business document.

MLS operates at the service-provider layer rather than the buyer-supplier communication layer. It allows the ASP receiving a document to report delivery and processing results back to the ASP that sent the document.

In the UAE framework, this communication occurs between:

• Supplier ASP (Corner 2)
• Buyer ASP (Corner 3)

The MLS message communicates what happened to the document after the recipient ASP received it and attempted to forward it to the final recipient.

The MLS specification defines three possible response outcomes:

• AB
• AP
• RE

UAE e-invoicing MLS AB AP RE codes help suppliers and their service providers understand whether a document was successfully delivered, forwarded without confirmation, or rejected.

The 3 Core MLS Status Codes - AB, AP, and RE

The MLS specification defines three response codes that communicate the delivery outcome of a business document. Each code represents a different processing result after the recipient ASP validates and attempts to forward the document. 

AB - Accepted Without Confirmation

An AB status means the recipient ASP forwarded the document to the final recipient but has no mechanism to verify whether the document arrived.

This status is used when communication between the recipient ASP and the final recipient does not support delivery confirmation.

Key points:

• The document was forwarded.
• The ASP attempted delivery.
• Delivery confirmation is unavailable.
• The recipient ASP cannot verify arrival.

AP - Accepted with Confirmation

An AP status indicates that the document was successfully delivered to the final recipient and the recipient ASP received verifiable confirmation of delivery.

This is the most definitive positive MLS outcome because it confirms successful transmission beyond the ASP layer.

Key points:

• The document reached the recipient.
• Delivery was successful.
• Confirmation was received.
• The ASP can verify delivery.

RE - Rejected

An RE status indicates that the document was not delivered to the final recipient for business processing.

The rejection occurs before successful delivery to the recipient and signals that processing could not continue.

Key points:

• Delivery did not occur.
• The document was not forwarded successfully for business processing.
• The sender receives notification through the MLS response.

How to Handle an RE Status

Public UAE e-invoicing guidance does not currently provide detailed correction procedures, resubmission timelines, or remediation workflows for MLS rejections.

When an RE status occurs, here's how to fix UAE e-invoice rejection:

1. Review the MLS response details.
2. Identify the issue reported by the ASP.
3. Correct the underlying invoice data or validation issue.
4. Follow the UAE e-invoice correction resubmission process defined by their ASP.
5. Maintain internal procedures for rejection handling and audit tracking.

Organizations should also work with their ASP for UAE e-invoicing error handling to understand implementation-specific correction and resubmission requirements.

How MLS Flows Through the UAE Peppol 5-Corner Model

Understanding the MLS flow helps clarify who generates the status message and when it is created within the UAE e-invoicing network.

The UAE e-invoicing model follows a 5-corner architecture:

The MLS process follows these steps:

Step 1: Supplier Sends the Invoice

The supplier creates an electronic invoice and submits it to its ASP.

Flow:

C1 → C2

Step 2: Supplier ASP Transmits the Document

The supplier ASP validates the document and sends it through the Peppol network to the recipient ASP.

Flow:

C2 → C3

Step 3: Buyer ASP Receives and Validates

The buyer ASP receives the document and performs the required validation checks.

At this stage, the ASP determines whether the document can proceed for delivery.

Step 4: Buyer ASP Attempts Delivery

The buyer ASP attempts to forward the document to the buyer.

Flow:

C3 → C4

The MLS specification requires the delivery attempt to occur before an MLS message is generated.

Step 5: Buyer ASP Determines the Outcome

After attempting delivery, the buyer ASP determines whether the outcome is:

• AP
• AB
• RE

The status depends on the delivery result and available confirmation information.

Step 6: MLS Message Is Generated

The buyer ASP generates the MLS message and sends it back to the supplier ASP.

Flow:

C3 → C2

This message contains the delivery outcome for the original document.

Step 7: Supplier Receives Status Information

The supplier ASP communicates the MLS result to the supplier.

Flow:

C2 → C1

The supplier can then take any required action based on the reported status.

MLS vs MLR - What's the Difference?

MLS and MLR are related concepts within the Peppol ecosystem, but they serve different purposes and operate between different participants.

MLS communicates delivery-related information between service providers.

MLR is used for business-level responses associated with business transactions and document processing.

Another important distinction is that MLS codes should be interpreted using MLS definitions.

Within MLS:

• AB = Accepted without confirmation
• AP = Accepted with confirmation
• RE = Rejected

These meanings should not be confused with similarly named codes that appear in other Peppol response contexts.