E-invoicing from SAP: SaaS solution or in-house development? The comparison for 2025

SaaS solution or in-house development: The right path to e-invoicing in SAP

From 2025, electronic invoicing will become mandatory in the B2B environment in Germany. Many companies that use SAP are therefore faced with a fundamental decision: Should e-invoicing be implemented directly in the SAP system as an in-house development, or is an external SaaS solution the more sensible option?

What initially appears to be a purely technical issue turns out, on closer inspection, to be a strategic decision. It is not just a matter of generating an XML document, but also of legal compliance, maintainability, international scalability, and long-term cost control.

This article highlights the differences between SaaS solutions and in-house development for e-invoicing in SAP. You will learn about the legal requirements, the risks and costs associated with in-house development, and why more and more companies are opting for a managed SaaS approach.

Why e-invoicing is now becoming mandatory

The basis for the e-invoicing requirement is EU Directive 2014/55/EU. The aim is to standardize invoice exchange within Europe, avoid media breaks, and make processes more efficient and transparent.

In Germany, this directive is being implemented gradually. From 2025, companies must be able to receive and process electronic invoices. In the following years (from 2027), structured dispatch will also become mandatory.

Specifically, this means the following for companies using SAP:

• Invoices must be in structured, machine-readable formats such as XRechnung or ZUGFeRD.
• PDF invoices without structured data sets no longer meet the requirements.
• The entire process—from creation and transmission to archiving—must be mapped in accordance with the law.

This makes sending invoices from SAP an integral part of compliance and digitization strategies. Companies that react too late or incorrectly risk delays in the payment process, additional accounting work, or, in the worst case, legal consequences.

In-house development in SAP – maximum control, but increasing complexity

Many companies initially consider developing their own SAP solution. The reasoning behind this is understandable: existing processes should be retained, forms adapted, and control kept entirely within the company’s own system.

An in-house development for e-invoicing in SAP offers definite advantages. Processes can be customized, existing output management structures can continue to be used, and adjustments appear flexible at first glance.

However, this is offset by considerable effort, which is often underestimated.

Typical advantages of in-house development

• High degree of process customization
• Direct access to code and logic
• Connection to existing SAP forms and workflows possible

Key challenges

The challenges lie primarily in the long-term perspective:

• High initial development costs in ABAP and SAP Output Management
• Ongoing maintenance costs by internal or external developers
• Dependence on the specific expertise of individual employees
• Regular adjustments in the event of changes to standards such as EN 16931 or new XRechnung versions

The dynamics of legal requirements are particularly critical. Formats, mandatory fields, and transmission channels change regularly. Every adjustment must be analyzed, developed, tested, and implemented. This ties up resources and increases the risk of errors in productive operation.

In addition, in-house developments often jeopardize the SAP Clean Core. Modifications and customer-specific enhancements complicate subsequent upgrades and increase the complexity of the overall system.

SaaS solution for e-invoicing in SAP – standardized and future-proof

A SaaS solution takes a fundamentally different approach. The e-invoicing process is not implemented in the SAP system itself, but is covered by an externally operated service that is seamlessly connected to SAP.

The big advantage lies in standardization. Legal requirements are implemented centrally and made available to all customers at the same time.

Advantages of a SaaS solution for e-invoicing from SAP

• Legal compliance from day one: Current requirements for XRechnung, ZUGFeRD, and international standards are already integrated.
• No development effort in the SAP system: The solution is ready for immediate use, without any transport or modifications.
• Automatic updates: Legal changes are implemented by the provider without the need for internal projects.
• International scalability: New countries and formats can be connected without additional implementations.
• Relief for the IT department: Operation, maintenance, monitoring, and archiving are handled by the SaaS provider.

This means that e-billing does not become a long-term project, but rather a stable, predictable process with clearly calculable costs.

SaaS solution or in-house development – a direct comparison

The differences are particularly clear when compared directly:

• Implementation: While an in-house development requires individual programming, a SaaS solution can be used immediately.
• Cost structure: In-house developments incur high initial investments and ongoing maintenance costs, while SaaS solutions offer predictable service fees.
• Compliance: With in-house developments, legal changes must be implemented manually, whereas with SaaS solutions, updates are performed automatically.
• Scalability: International requirements are complex for in-house developments, whereas SaaS solutions are designed to be cross-border from the outset.
• System stability: In-house developments can compromise the SAP Clean Core, whereas SaaS solutions do not require any intervention in the core system.

For companies that value long-term stability, legal certainty, and low internal costs, there are many arguments in favor of a SaaS approach.

Softway’s Global E-Invoice Cloud as a SaaS approach for SAP

With Global E-Invoice Cloud, Softway AG offers a managed SaaS solution that is specifically tailored to the requirements of SAP users.

Die Lösung deckt den gesamten Prozess ab – von der Erzeugung strukturierter Rechnungsdaten über die rechtskonforme Übermittlung bis hin zur Archivierung.

Key features of the Global E-Invoice Cloud:

• Cloud-based operation without an additional SAP contract
• Ready-to-run integration into existing SAP systems
• Automatic archiving in accordance with legal requirements
• Support for international e-invoice formats
• Full legal compliance according to EN 16931

This provides companies with a future-proof solution that meets growing regulatory requirements without placing unnecessary strain on internal IT resources.

Conclusion: SaaS solution as a sustainable path to e-invoicing in SAP

The mandatory use of e-invoicing from 2025 onwards makes it clear that short-term transitional solutions are not sufficient. Companies must make a decision that will remain valid in the coming years.

Although an in-house development in SAP offers individual design options, it involves high costs, ongoing expenses, and compliance risks.

A SaaS solution for e-invoicing in SAP, on the other hand, ensures legal compliance, scalability, and reduces the burden on internal resources. Especially in view of international requirements and future legal changes, a managed SaaS approach is the more sustainable option for many companies.