Clean Core vs. Customisation: What CIOs Really Need to Know Before an S/4HANA Move
For organisations preparing to transition to SAP S/4HANA, the conversation often starts with fit-to-standard embracing SAP best practices, minimising customisation, and staying clean. But beneath this simplified narrative lies a far more complex balancing act the trade-off between long-term maintainability and the need for agility, differentiation, and control.
For CIOs and CFOs, getting this right is not just an implementation detail; it’s a strategic decision that will shape the business’s digital resilience for a decade or more.
Why “Clean Core” Has Become the New Standard
SAP’s clean core strategy is about future-proofing. By minimising custom code in the S/4HANA core, organisations gain easier access to cloud updates, lower technical debt, and faster innovation cycles. This model aligns perfectly with SAP’s shift toward modular, composable ERP where extensibility happens outside the core using tools like SAP BTP, side-by-side development, or low-code platforms.
From a technical standpoint, the benefits are compelling. Fewer modifications mean smoother upgrades, fewer regression bugs, and easier integration with the broader SAP ecosystem. From a financial perspective, clean core reduces total cost of ownership over time and provides more predictable system maintenance and support.
But Clean Core Is Not One-Size-Fits-All
For many organisations, especially those with complex, differentiated processes strict adherence to standard functionality is neither practical nor desirable. Certain industry requirements, regulatory rules, or competitive capabilities simply can’t be delivered by out-of-the-box SAP solutions. In these cases, insisting on fit-to-standard can lead to inefficiencies, workarounds, or degraded user experiences that undercut the very value the transformation was meant to deliver.
This is where the “clean core” conversation needs to evolve. The real question is not whether to customise, but where, why, and how to do it in a way that balances innovation with sustainability.
A Decision Framework for Customisation
To help CIOs and CFOs evaluate when customisation is justified, consider a three-lens decision framework:
Strategic Value: Does the process or capability create measurable business differentiation? If a function is mission-critical and gives your organisation a competitive edge such as pricing logic, customer experience workflows, or regulatory reporting—customisation may be the right investment.
Process Maturity: Is the current process optimised and stable, or does it need transformation? Customising a broken or inefficient process simply hardcodes dysfunction. In contrast, well-understood and value-generating processes are better candidates for tailored enhancements.
Lifecycle Alignment: Will the customisation endure through multiple SAP updates, or is it addressing a temporary gap? Strategic customisation should be built for longevity, ideally decoupled from the core via extensibility platforms like SAP BTP.
This framework helps move the conversation from ideology to evidence ensuring customisation is a business decision, not a developer preference.
The Hidden Risks of Over-Customisation
While there are clear justifications for selective enhancements, unchecked customisation remains one of the biggest risks in an S/4HANA program. Legacy ECC environments often suffered from years of technical sprawl, with undocumented code, performance issues, and upgrade blockers.
These patterns are easily repeated if guardrails aren’t put in place early in the design phase. Without strong governance, even well-intentioned modifications can quickly erode the upgradeability and agility that clean core promises. These issues may not emerge until years later when supportability and total cost of ownership become harder to control.
When Customisation Still Makes Strategic Sense
There are cases where customisation isn’t just justifiable, it’s essential. Highly regulated industries may need country-specific compliance logic that standard SAP doesn’t yet support. Consumer-facing businesses may require unique integrations or customer journeys that drive loyalty and revenue.
In these scenarios, the priority should be clean architecture, not just clean core. That means using SAP BTP for side-by-side extensions, leveraging APIs for interoperability, and avoiding modifications to the digital core wherever possible. The goal is to enable strategic flexibility without compromising technical integrity.
Clean Core as a Journey, not a Destination
Ultimately, clean core is not a binary choice it’s a maturity model. Most organisations will land somewhere on the spectrum, with a mix of standard functionality, side-by-side extensions, and limited core customisations. What matters is having a clear strategy for where each type of functionality belongs, and why.
CIOs and CFOs should treat this as an ongoing governance discussion, not a one-off implementation milestone. That includes regular reviews of technical debt, upgrade readiness, and the business value of custom extensions. With the right architecture and mindset, it’s possible to build a flexible, forward-compatible SAP landscape without sacrificing what makes your business unique.
Aligning Technology with Business Strategy
The S/4HANA transformation is as much a leadership challenge as it is a technical one. CIOs and CFOs must work together to define what “standard” means in their context and where differentiation drives real value. Clean core isn’t about rigid conformity, it’s about architectural discipline that enables change at speed. When done right, it gives you the best of both worlds: a stable foundation for the future and the agility to adapt as your business evolves.