Page tree

European Commission Digital

eInvoicing Documentation

Message Transport

Directive 2014/55/EU on electronic invoicing in public procurement identifies message transport as one of three levels of eInvoicing interoperability.

In simple terms, to be able to exchange and automatically process eInvoices that comply with the European standard, the seller and buyer must have a connection that allows them to exchange eInvoices in a way that is reliable and makes their automated processing possible.

EInvoicing transport also plays an important role in fulfilling the following legal requirements.

Legal requirements

An invoice must fulfil certain requirements in order to be accepted as a basis for the financial records of an organisation. Additionally, an invoice must fulfil certain requirements to be accepted as a basis for value-added tax (VAT) reporting. The Directive 2006/112/EC on the common system of value-added tax defines the following criteria:

Article 233 of VAT Directive 2006/112 

1. The authenticity of the origin, the integrity of the content and the legibility of an invoice, whether on paper or in electronic form, shall be ensured from the point in time of issue until the end of the period for storage of the invoice.

Each taxable person shall determine the way to ensure the authenticity of the origin, the integrity of the content and the legibility of the invoice. This may be achieved by any business controls which create a reliable audit trail between an invoice and a supply of goods or services.

‘Authenticity of the origin’ means the assurance of the identity of the supplier or the issuer of the invoice.
‘Integrity of the content’ means that the content required according to this Directive has not been altered.

2. Other than by way of the type of business controls described in paragraph 1, the following are examples of technologies that ensure the authenticity of the origin and the integrity of the content of an electronic

(a) an advanced electronic signature within the meaning of point (2) of Article 2 of Directive 1999/93/EC on a community framework for electronic signatures (1), based on a qualified certificate and created by a secure signature creation device, within the meaning of points (6) and (10) of Article 2 of Directive 1999/93/EC;

(b) electronic data interchange (EDI), as defined in Article 2 of Annex 1 to Commission Recommendation 1994/820/EC relating to the legal aspects of electronic data interchange (1), where the agreement relating to the exchange provides for the use of procedures guaranteeing the authenticity of the origin and integrity of the data

The eInvoicing standard guideline on interoperability on transmission level identifies several topics that are relevant for the transmission of electronic invoices and provides guidelines on best practices.


A key objective of the European standard on eInvoicing is to facilitate interoperability on the invoice document level. This interoperability fails if the different parties can not exchange these invoices through interoperable messaging networks. Transport of electronic messages can be handled by the parties themselves or through message transport services that are widely available in a competitive environment. These services offer technical solutions for transferring electronic messages using different technologies and often sold with additional value-added services. These different messaging services can be grouped into three main operating models, where the providers of the same service may offer different services using one or a combination of those models.

Direct connections (two-corner model)

In a direct connection or two-corner model, the buyer and the seller connect directly. In this model, one party sets up identical connections with multiple parties but each connection only allows him to communicate with one specific party.

Transmission hub (three-corner model)

In the transmission hub or three corner model, there is a hub (typically operated by a service provider) that links multiple parties connected to the same hub. In this model, each party only needs to set up a single connection to this hub. Through this unique connection, the party can communicate with any other party connected to the same hub. As new parties connect to the hub over time, they can communicate with all existing connecting parties.

Roaming network (four-corner model)

In a roaming network or four corner model, different hubs are connected together through a roaming network or protocol. This allows communication with all parties connected to the same hub and others, connected to other hubs who are linked through the roaming network and use interoperable protocols.

These different operating models are shown in the following diagram.

Transmission network models Copy

Public Authorities choice of operating model

A Public Authority choice of an operating model depends on its needs for connections.

If the Public Authority only needs to make a few connections that change infrequently then a direct connection should be the best choice.

A large Public Authority that operates in a specific trading area may benefit from operating its own hub to which its trading partners will connect in a 3-corner model. However, the Public Authority needs to communicate to a larger group of trading partners that may be using other hubs and/or change service providers over time. In this case, there is a benefit of using a hub that has a roaming connection. A Public Authority can also connect to a roaming network through a contracted service provider instead of operating its own hub. An example of roaming networks is the eDelivery and Peppol networks.

Network structures Copy

Message transport examples

Specifications for an interoperable message exchange network, as the reusable component


What is eDelivery

eDelivery is a network of nodes for digital communications. It is based on a distributed model where every participant becomes a node using standard transport protocols (based on AS4) and security policies. eDelivery helps public administrations to exchange electronic data and documents with other public administrations, businesses and citizens, in an interoperable, secure, reliable and trusted way. eDelivery is one of the building blocks of the DIGITAL programme.

Global Interoperability Framework (GIF)

What is GIF

The GIF builds on the concept that ‘interoperability can be organized through the linkage of trading parties irrespective of the specific information technology environment or eInvoicing solution or service used by each trading party’. The GIF does not propose a single network but offers a blueprint for interoperability solutions based on the common use of recommended standards and practices. Both the GIF and the interoperability solutions offered or being developed by its constituent associations recommend the use of the eDelivery components (e.g. AS4, SML/SMP). GIF is proposed by a group of European and North American associations and builds on previous work undertaken by OpenPEPPOL, EESPA and the Business Payments Coalition (US) organized by the Federal Reserve Bank of Minneapolis, which together with Connect ONCE are the initial members of the GIF Working Group.

Benefits of GIF

The GIF enables different scheme organizers to benefit from the flexibility when setting up the governance and business practices according to their community requirements and culture, all based on consistently implemented technical standards.

Implements eDelivery specifications in their network, instantiations of eDelivery networks


What is OpenPEPPOL

OpenPEPPOL is a non-profit international association whose purpose it is to enable European businesses to easily deal electronically with any European public sector buyers in their procurement processes.

Benefits of OpenPEPPOL

OpenPEPPOL is dedicated for procurement with the public sector and includes a network over 150 service providers in over 20 countries of Europe enabling message roaming between any of them.

A list of OpenPEPPOL service providers can be found at