A Practical Guide to Upgrade-Safe Extensibility (and How to Train Teams)
SAP S/4HANA programmes are increasingly shaped by one principle. Clean core is now central to long-term system strategy.
However, many organisations still struggle to apply it in practice. In particular, the SAP clean core levels A–D model is not always well understood.
Is this the end of customisations? How should organisations use clean core levels to support upgrade-safe extensibility, and how should teams be trained? This paper explores these questions.
What Are SAP Clean Core Levels A–D?
SAP defines clean core as keeping the core system as standard as possible. Extensions are then built outside the core using approved methods.
To support this, SAP introduced clean core levels A–D. These levels classify how closely extensions align with upgrade-safe principles.
At a high level, Level A represents fully compliant, upgrade-safe extensions. In contrast, Level D includes modifications that risk breaking during upgrades.
Therefore, the model provides a practical framework for decision-making.
Why Clean Core Matters for S/4HANA Extensibility
Extensibility is essential in most ERP programmes. Organisations still need to meet specific business requirements.
However, traditional customisation creates long-term issues. These include upgrade complexity, higher costs, and reduced agility. Clean core addresses this challenge.
By separating extensions from the core, organisations can adopt standard SAP updates more easily. As a result, systems remain stable and future-ready. According to SAP guidance, clean core is a key enabler of continuous innovation in S/4HANA.
In addition, PwC highlights that clean core strategies reduce technical debt and support faster transformation cycles.
Understanding Levels A–D in Practice
While the concept is straightforward, applying it requires clarity.
Level A includes side-by-side extensions using SAP Business Technology Platform. These are fully upgrade-safe.
Level B includes in-app extensibility using approved SAP tools. These remain largely compliant with clean core principles.
Level C includes enhancements that introduce some risk. These may require adjustment during upgrades.
Level D includes direct modifications to the core. These are not upgrade-safe and should be avoided.
This classification helps organisations prioritise remediation activities. It also supports governance during programme delivery.
The Hidden Risk: Misalignment Between Design and Adoption
Many organisations define clean core strategies at design stage. However, challenges often emerge during adoption.
Users may revert to legacy processes. In addition, workarounds may introduce unintended complexity. This creates a gap between design intent and operational reality. Research from Deloitte shows that governance and user behaviour are key risks in ERP transformation.
Therefore, clean core is not only a technical concept. It is also a behavioural one.
Why Training Is Critical for Clean Core Success
Clean core requires users to work within standard processes. This often differs from legacy SAP ECC environments.
As a result, training specific to your organisation and programme becomes essential. Users must understand not only how processes work, but also why standardisation matters. Without this understanding, there is a risk of resistance or workaround behaviour.
iTrain’s experience across S/4HANA programmes shows that early training improves alignment with clean core principles. You can explore structured SAP training approaches here:
The organisational change this entails requires careful management. Whilst programmes often focus on managing the technical change required the transformation of staff can be a side task – both should take equal footing to ensure programme success.
iTrain partner with our clients to provide a fully integrated service. You can find more information on Change Management services here:
Enabling Learning with SAP Enable Now
Digital learning tools play an important role in clean core adoption.
SAP Enable Now supports in-system guidance and contextual learning. This helps users follow standard processes in real time.
In addition, it reinforces correct behaviours after go-live.
This is particularly valuable where processes are changing significantly.
Embedding Clean Core into Testing
User Acceptance Testing is another critical control point.
Testing should validate not only functionality, but also adherence to clean core principles.
For example, test scenarios should confirm that standard processes are followed. They should also identify deviations early.
This approach reduces the risk of introducing non-compliant solutions.
iTrain’s integrated approach supports this alignment.
Lessons from ERP Transformation Programmes
Experience across ERP programmes highlights a consistent theme.
Clean core strategies succeed when supported by training, governance, and testing. For example, iTrain case studies demonstrate that structured enablement improves adoption outcomes.
You can explore examples here:
In contrast, programmes that focus only on technical design often encounter challenges post go-live. These challenges typically relate to user behaviour rather than system capability.
What Organisations Should Do Now
Organisations should take a structured approach to clean core adoption.
Firstly, assess current extensions against the A–D model. This provides visibility of risk.
Secondly, define governance to control future development. This ensures alignment with clean core principles.
In addition, invest in training and user enablement. This supports behavioural change.
Finally, align testing, training, and design. Integration is essential for success.
Contact iTrain Today
Clean core is not only a design principle. It is an operational discipline that depends on user behaviour.
iTrain supports organisations delivering SAP S/4HANA programmes with a focus on clean core enablement.
Our approach combines company specific designed role-based training, digital learning, and structured testing.
Whether you are defining your clean core strategy or already in delivery, early preparation reduces risk.
To discuss your programme, contact iTrain today.