SAP Clean Core Extensibility: A Practical, Risk-Based Guide For Modern Consultants (2026 Edition)

Q: Is SAP Clean Core Extensibility anti-customisation?

No. It promotes responsible customisation using released, upgrade-safe mechanisms.

In the world of SAP consulting, most of us have encountered it at least once: an ERP landscape so heavily customised that even the word “upgrade” is enough to make a project team uneasy. Over time, SAP systems often accumulate undocumented changes, tightly coupled custom code, and fragile integrations. The result is reduced flexibility, rising upgrade effort, and an ever-increasing total cost of ownership.

To address this reality, SAP has refined its SAP Clean Core Extensibility strategy. Rather than framing systems as simply “clean” or “unclean,” SAP now promotes a pragmatic, risk-based maturity model that allows customers to modernise at a realistic pace—without jeopardising stability.

This article serves as a consultant’s guide to understanding how to design, build, and modernise SAP systems while keeping the digital core clean, resilient, and ready for innovation.

Table of Contents

Why SAP Clean Core Extensibility Is the Modern Consultant’s Mandate

The pace of enterprise technology change has accelerated dramatically. Innovations such as Business AI, event-driven architectures, and continuous cloud upgrades demand an ERP core that can evolve quickly and safely.

Legacy on-premise systems, however, often suffer from:

Excessive customisation
Low process standardisation
Inconsistent data quality
High dependency on internal SAP objects

These issues create friction whenever organisations attempt to adopt new SAP capabilities.

A SAP Clean Core Extensibility approach changes the dynamic. Instead of modifying the ERP core to fit every business requirement, the model encourages:

Alignment with SAP best-practice processes
Decoupling custom logic from the core
Using released APIs and stable extension frameworks

For consultants, this shift is critical. It allows us to help customers reduce technical debt, shorten innovation cycles, and redirect IT spend from maintenance to value creation. In short, Clean Core is not about limiting flexibility—it is about enabling sustainable flexibility.

The Five Guiding Principles of a Clean Core

Although Clean Core discussions often focus on code, the concept is much broader. SAP defines five interdependent pillars that together determine the health of an ERP landscape.

1. Business Processes

Standardised processes reduce complexity, ease upgrades, and improve user adoption. Deviations from standard should only exist where they provide clear business differentiation.

2. Extensibility

All extensions should be decoupled from the SAP core using released frameworks and APIs. This ensures upgrade stability and long-term maintainability.

3. Data

Clean data models, governed master data, and compliance with SAP data standards are essential. Poor data quality undermines automation, analytics, and AI initiatives.

4. Integration

Modern integration relies on released APIs, events, and asynchronous messaging rather than point-to-point connections or direct table access.

5. Operations

Clean Core is sustained through disciplined operations—automated testing, transport controls, monitoring, and lifecycle management.

These pillars reinforce one another. For example, clean extensibility depends on operational controls such as mandatory code checks and testing during the development lifecycle.

Understanding the SAP Clean Core Extensibility Levels (A–D)

One of the most important evolutions in SAP’s strategy is the move from a simple three-tier model to a four-level Clean Core maturity framework. This allows consultants to assess extensions with far greater precision.

Level A – The Gold Standard

Level A extensions use only publicly released and upgrade-stable interfaces backed by formal SAP stability contracts.

Typical examples include:

ABAP Cloud on-stack extensions
Side-by-side extensions on SAP BTP
SAP Build applications and workflows

Level A represents the target state. These extensions are future-ready, cloud-compliant, and fully aligned with SAP’s roadmap.

Level B – Classic APIs

Sometimes, Level A interfaces are not yet available. Level B allows the use of well-defined classic SAP APIs, such as BAPIs, that are documented and generally upgrade-stable.

While not ideal, Level B is acceptable when:

No released API exists
Risk is understood and documented
Automated testing is in place

Level C – Internal SAP Objects

Level C is considered “conditionally clean.” It involves using internal SAP objects that are not officially released.

SAP mitigates some of this risk through the SAP Object Change Log, which allows teams to anticipate breaking changes. However, these extensions require:

Strong monitoring
Refactoring plans
Clear ownership

Level D – Not Recommended

Level D represents the highest risk and should be avoided whenever possible. Examples include:

Modifications to SAP standard objects
Direct database table writes
Implicit enhancements

These practices create significant technical debt and should be prioritised for remediation.

Choosing the Right Architecture: On-Stack vs Side-by-Side

A core responsibility of SAP consultants is deciding where an extension belongs.

On-Stack Extensibility

On-stack extensions are justified when:

Transactional consistency is critical
Large data volumes require complex SQL
Tight coupling with core processes is unavoidable

In these cases, ABAP Cloud is mandatory to maintain compliance with SAP Clean Core Extensibility standards.

Side-by-Side Extensibility

Side-by-side extensions on SAP BTP are preferred when:

Processes are loosely coupled
External users are involved
Innovation speed is a priority

With SAP Build and tools like Joule, SAP’s AI copilot, consultants can now design applications, workflows, and integrations faster than ever—without compromising core stability.

The Methodology: “Get Clean” and “Stay Clean”

Clean Core is not a one-time project; it is a continuous discipline.

Stay Clean: Preventing New Technical Debt

Every new requirement should be challenged:

Does it deliver real business differentiation?
Can standard SAP functionality meet the need?
Is a certified partner add-on available?

Many organisations formalise this governance through a Solution Standardisation Board (SSB) that reviews and approves deviations.

Get Clean: Reducing Existing Debt

Using RISE with SAP and SAP Cloud ALM, teams can:

Identify unused custom code
Analyse modification hotspots
Track Clean Core maturity over time

A practical approach is setting incremental goals, such as reducing technical debt by 10% per year. Applying the “boy scout principle”—leaving code cleaner than you found it—ensures continuous improvement without disruptive clean-up projects.

Measuring Clean Core Success with KPIs

Effective governance requires measurable outcomes. SAP’s Clean Core Measurement Framework includes key indicators such as:

Clean Core Share: Distribution of objects across Levels A–D
Technical Debt Score: Weighted ATC findings (e.g. errors vs warnings)
Unused Code Share: Custom objects no longer in use
Business Modifications: Changes to standard code outside released extension points

These KPIs turn Clean Core from a concept into a manageable program

Governance and Enforcement: Making Clean Core Stick

Guidelines alone are not enough. Successful organisations enforce Clean Core through technical controls, including:

Restricting ABAP language versions via authorisations
Mandatory ATC checks during transport release
Blocking transports with critical findings unless formally exempted
Automated ABAP Unit tests, especially for Levels B, C, and D

This shifts Clean Core from “best effort” to standard operating procedure.

Conclusion: Clean Core as a Strategic Journey

Transitioning to SAP Clean Core Extensibility is a marathon, not a sprint. It requires a mindset shift—treating code as a strategic asset, not just a technical solution.

By upskilling teams from classic ABAP to ABAP Cloud, leveraging SAP Cloud ALM, and embracing SAP BTP, consultants can help customers build landscapes that are agile, resilient, and innovation-ready.

The goal is not to eliminate customisation, but to ensure every extension delivers business value without compromising the integrity

Frequently Asked Questions (FAQs)

Is SAP Clean Core Extensibility anti-customisation?

No. It promotes responsible customisation using released, upgrade-safe mechanisms.

Can existing systems ever reach Level A completely?

In practice, most landscapes will be mixed. The goal is continuous improvement, not perfection.

Is ABAP Cloud mandatory for S/4HANA?

ABAP Cloud is mandatory for new on-stack extensions if Level A compliance is required

How does Clean Core support Business AI?

AI relies on clean data models, stable APIs, and upgrade-safe processes—all enabled by Clean Core.

.What role does SAP BTP play?

SAP BTP is the preferred platform for side-by-side extensibility and innovation.

How long does a Clean Core transformation take?

It is an ongoing journey, typically executed incrementally over several years.

Share on Facebook

SAP Clean Core Extensibility: A Practical, Risk-Based Guide for Modern Consultants (2026 Edition)

Why SAP Clean Core Extensibility Is the Modern Consultant’s Mandate