Copy to Bookkeeper: bringing accounting document exchange into Peppol

Peppol has become the standard way to exchange electronic invoices between suppliers and buyers. But in practice, the invoice journey often does not stop there: businesses also need to make their incoming and outgoing invoices available to their accountants or bookkeepers. Today, this part of the process is still frequently handled through proprietary APIs, accounting portals, file exports, email or private document exchange networks.

The Peppol Copy to Bookkeeper process addresses this gap by providing a standardized way to exchange accounting copies of billing documents through the Peppol network.

The idea is simple: allow businesses and their software providers to send an unchanged copy of Peppol billing documents to their accountant or bookkeeper through the Peppol network itself, using a standardized process.

For software vendors and Peppol Access Points, this standardized process reduces the need for bilateral integrations. For accounting firms, it provides a more consistent and automated way to receive client documents.

Digiteal currently leads the Belgian Peppol focus group working on third-party scenarios and has coordinated the Copy to Bookkeeper RFC together with Belgian and European Peppol experts.

What is Copy to Bookkeeper?

Copy to Bookkeeper is a proposed Peppol process for sending a copy of an existing billing document to an accountant or bookkeeper.

The key point is that the accounting copy is not a new invoice: it is the same business document, transported through Peppol for a different business purpose. The original supplier, customer, amounts, VAT information and other invoice data remain unchanged.

What changes is the transport context: instead of delivering the document as part of the normal supplier-to-customer billing process, Peppol is used to transport a copy to the bookkeeping party. This distinction is a fundamental principle of the Copy to Bookkeeper architecture.

Why is Copy to Bookkeeper needed?

The traditional Peppol billing flow is straightforward: the supplier sends an invoice through its access point. The invoice is delivered through the network to the buyer’s access point and ultimately reaches the buyer’s software.

But accounting processes involve more parties. A supplier may use an ERP or invoicing solution to issue invoices while its accounting is handled by another platform or by an external accounting firm. A buyer may receive invoices in an ERP, procurement system or document management solution while those same invoices also need to reach its accounting environment.

As a result, software vendors have had to solve this problem outside Peppol. That can mean building direct integrations with accounting platforms, exposing APIs, exchanging documents through private networks or asking customers to manually export and transfer invoices. These approaches can work but they do not scale particularly well.

Every new software-to-software connection potentially requires another integration, another authentication model, another mapping and another maintenance relationship. Copy to Bookkeeper aims to replace part of that complexity with a standardized Peppol flow.

How does Copy to Bookkeeper work?

Diagram illustrating the Copy to Bookkeeper Peppol flow for exchanging accounting documents with bookkeepers

Imagine a supplier creates an invoice for a customer. The normal Peppol flow remains unchanged: the supplier sends the invoice to the buyer through Peppol using the standard billing process.

Now assume the supplier also wants the same invoice to reach its accounting software or external bookkeeper. A second Peppol transmission can take place: supplier ➡️ supplier’s bookkeeper. The payload remains the original invoice.

Similarly, on the buyer side, an invoice received through Peppol can subsequently be forwarded to the buyer’s bookkeeping environment: buyer ➡️ buyer’s bookkeeper. Again, the document itself remains unchanged.

This mechanism is implemented through a dedicated Peppol BIS Copy flow, derived from the existing Billing process but governed by specific rules that allow billing documents to be transported to third parties.

This enables Peppol to become not only the transport mechanism between trading partners but also a standardized transport mechanism between businesses and the parties managing their bookkeeping.

The technical principle

From a technical perspective, Copy to Bookkeeper introduces an interesting difference compared with normal BIS Billing exchanges.

In a standard Peppol billing transaction, the sender and receiver identified in the transport envelope are expected to correspond to the business parties represented inside the document. That makes perfect sense when an invoice moves directly from supplier to customer but it does not work for a copy scenario.

If a buyer receives an invoice and subsequently sends that invoice to its bookkeeper, the buyer becomes the sender of the Peppol message even though the supplier remains the supplier inside the invoice. Likewise, the receiving Peppol participant is now the bookkeeper while the customer inside the invoice remains unchanged.

The Copy to Bookkeeper process relies on two fundamental technical elements:

A dedicated Process Identifier identifies the Copy to Bookkeeper exchange using the process name ‘bookkeeping’
A specific exception to the Peppol ‘Compliance to BIS’ rules allows the sender and receiver identifiers in the SBDH transport envelope to differ from the corresponding EndpointID values inside the business document. This enables the original billing document to be transported unchanged while clearly identifying the exchange as an accounting copy.

More than invoices

Although invoices are the most obvious use case, Copy to Bookkeeper covers a broader range of billing-related documents including invoices, credit notes, self-billing documents and invoice responses, with the relevant role adjustments. This matters because accounting workflows do not consist only of invoices.

By supporting multiple billing-related document types, Copy to Bookkeeper provides a foundation for more complete accounting document exchanges within the Peppol ecosystem rather than introducing another isolated invoice-only mechanism.

Why this matters for software vendors

For ERP vendors, invoicing platforms and accounting software providers, Copy to Bookkeeper introduces a standardized mechanism that significantly simplifies interoperability between business and accounting applications.

Today, a software vendor wanting to transfer documents to accounting environments may have to support several proprietary APIs or document exchange mechanisms. A standardized Peppol process changes the model. Instead of asking ‘How do I integrate with accounting platform A, B or C?’, the question can increasingly become: ‘Can the accounting environment receive this Peppol process?’. That opens the door to a much more scalable architecture.

A software vendor could implement one standardized mechanism and make it available to many accounting environments, provided the relevant access points and receiving applications support the process. This also gives vendors the opportunity to offer a better user experience. For example, a business could configure its accountant once and have incoming and outgoing billing documents automatically forwarded without requiring manual downloads, uploads or email exchanges.

Why this matters for Peppol Access Points

Access Points are the second essential link in the chain. Even if an ERP or accounting solution supports Copy to Bookkeeper at application level, the Peppol infrastructure must also be able to transport the new process.

Access Points will therefore need to understand and support the dedicated Process Identifier and correctly handle the associated transport rules.

On the sending side, an access point may need to send an unchanged document on behalf of a customer to the customer’s bookkeeper. On the receiving side, an access point serving accountants or accounting platforms must be ready to advertise and process the new receiving capability. This is particularly important because support for the Copy to Bookkeeper process is optional.

Not every Peppol participant or access point needs Copy to Bookkeeper. The process is primarily relevant to service providers whose customers include businesses, accounting applications, accountants or bookkeepers. That makes early coordination between software vendors and Access Points especially valuable.

What do accountants and bookkeepers gain?

For accounting firms, the benefit is straightforward: documents can arrive automatically through a standardized network. Instead of asking each customer which ERP they use, which portal they need to connect to or which export format is available, an accounting environment could receive documents through Peppol. This can reduce manual document collection and lower the dependency on proprietary integrations. It can also make onboarding new customers easier.

If both sides support the process, the accounting firm no longer needs a bespoke integration with every invoicing solution used by its clients. For larger accounting platforms serving thousands of businesses, that interoperability benefit can become significant.

Why not just send the invoice twice?

It is important to distinguish Copy to Bookkeeper from simply issuing or sending the same invoice twice.

The accounting copy is not another commercial invoice sent to another buyer; it is a copy of an existing business document transported for a different purpose.

That is precisely why Copy to Bookkeeper uses a separate Peppol process. Its dedicated Process Identifier makes the intent explicit and allows software and access points to distinguish an accounting copy from the normal billing flow. It also avoids changing the invoice itself merely to make the transport possible.

From Belgian initiative to Peppol standardization

Copy to Bookkeeper originated from the work of the Belgian Peppol Service Provider Forum, which established a dedicated focus group to address third-party scenarios within the Peppol ecosystem.

These scenarios include exchanges involving factoring companies, accountants, bookkeepers and buyer agents, where business documents need to be transported to parties other than the original supplier or buyer.

Digiteal leads this Belgian focus group and coordinates the Copy to Bookkeeper initiative in collaboration with Belgian and European Peppol experts.

Building on this collaborative work, Copy to Bookkeeper was formalized through an OpenPeppol Request for Change (see also the underlying RFC document) defining the architectural principles required to exchange unchanged billing documents with accounting parties.

Following its approval through the OpenPeppol governance process, Copy to Bookkeeper provides a standardized framework for these exchanges including a dedicated Process Identifier and specific transport rules.

This represents an important step towards extending Peppol interoperability beyond traditional supplier-to-buyer document exchanges.

An important building block for the evolution of Peppol

Copy to Bookkeeper addresses a very practical accounting challenge while introducing architectural principles that can also be relevant to other third-party scenarios.

Peppol was originally designed primarily around exchanges between business parties. Modern document flows, however, increasingly involve additional actors. Accountants are one example, factoring companies are another, and buyer agents are yet another.

The Belgian third-party scenarios focus group is investigating these use cases in parallel. The Belgian forum notes indicate that factoring still requires additional business stakeholder input, while the buyer-agent scenario may potentially reuse the copy mechanism being designed for accounting. Copy to Bookkeeper therefore establishes an important foundation for addressing additional third-party scenarios within the Peppol ecosystem.

With Copy to Bookkeeper, Peppol provides a standardized approach for transporting copies of billing documents to authorized third parties. The underlying architectural principles also create opportunities to address other business processes involving additional participants.

From standardization to implementation

With the Copy to Bookkeeper process standardized, software vendors and Peppol Access Points can begin implementing the necessary capabilities to support accounting document exchanges through Peppol.

Important implementation questions include:

How will customers configure their bookkeeper?
How will the receiving Peppol participant be identified?
How will the dedicated process be advertised in the SMP?
How will outgoing and incoming copies be triggered?
How will duplicate processing be avoided?
How will copies be distinguished from normal billing transactions?
How will accounting applications route the received document to the correct customer file?

These questions involve the complete chain from business software to Access Point to receiving accounting applications. This is why cooperation between software vendors and Peppol Service Providers will be critical to adoption. An implementation guide is in the works to answer all of those questions.

How Digiteal can help

Digiteal leads the Belgian Peppol focus group working on third-party scenarios and plays a leading role in the development and standardization of the Copy to Bookkeeper process, together with Belgian and European Peppol experts. This involvement gives Digiteal first-hand expertise in the business requirements, technical architecture and implementation principles of Copy to Bookkeeper.

For software vendors and Peppol Access Points looking to implement Copy to Bookkeeper, Digiteal can help assess the impact on existing Peppol flows, understand the technical requirements, adapt their infrastructure and integrate the standardized process into their solutions.
Whether you are an ERP vendor, an accounting software provider or a Peppol Access Point, Digiteal can support your adoption of Copy to Bookkeeper and help you take advantage of this new interoperability capability.
For the Peppol ecosystem, Copy to Bookkeeper represents something broader than a new document route: it is an opportunity to replace another layer of proprietary integrations with interoperable infrastructure and to extend the value of Peppol beyond the traditional supplier-to-buyer exchange.