IT directors at companies still running SAP ECC need to act now: SAP ends mainstream maintenance for ECC on December 31, 2027, meaning no more security patches, bug fixes, or legal updates after that date. For most organisations, migrating to SAP S/4HANA is the only realistic path forward. The questions below cover what that transition actually involves, how long it takes, and where the real risks lie.
What happens to SAP ECC after the 2027 deadline?
After December 31, 2027, SAP will no longer provide standard support for ECC, including security patches, regulatory updates, and bug fixes. Organisations that stay on ECC beyond this date will be running unsupported software, which creates serious compliance, security, and operational risks. SAP has made clear that extended maintenance options exist but come at a significant additional cost.
Running unsupported ERP software is not just a technical inconvenience. It means your system will not automatically comply with changes in tax law, financial reporting standards, or data protection regulations. It also means any vulnerabilities discovered after the deadline will remain unpatched unless you pay for a costly extended support arrangement. For most organisations, this makes staying on ECC a short-term option at best, not a long-term strategy.
The business case for moving to SAP S/4HANA is therefore not only about new functionality. It is about maintaining a stable, compliant, and secure operational foundation. Organisations that delay too long risk entering the migration process under pressure, which is exactly when mistakes happen.
How much time does an SAP S/4HANA migration actually take?
An SAP S/4HANA migration typically takes between 12 and 36 months, depending on the size of the organisation, the complexity of existing processes, the chosen migration approach, and the availability of internal resources. Smaller, more standardised environments can move faster. Large multinationals with customised ECC landscapes and multiple business units should plan for significantly longer timelines.
The most common mistake organisations make is underestimating how much time the preparation phase requires. Before any technical migration work begins, you need a clear picture of your current landscape: what data exists, how processes are configured, where customisations sit, and what the target state looks like. This preparation work directly determines how smooth the actual migration will be.
With the 2027 deadline approaching and 2026 already here, organisations that have not yet started are working with limited runway. A 24-month migration that begins in mid-2026 lands right at the deadline with no buffer for delays. Starting with a structured baseline assessment of your current ERP maturity is one of the most practical things you can do right now to understand where you stand and how much time you realistically need.
What’s the difference between a greenfield and brownfield SAP migration?
A greenfield migration means building your SAP S/4HANA environment from scratch, without carrying over existing configurations, customisations, or historical data structures. A brownfield migration means converting your existing ECC system to S/4HANA, preserving your current setup, data, and configurations as the starting point. The right choice depends on how much of your current ECC landscape you want to keep.
Greenfield: starting fresh
Greenfield is the right approach when your current ECC system is heavily customised, when you want to redesign core business processes, or when your organisation has outgrown its existing configuration. It gives you a clean slate and the opportunity to adopt SAP best practices without legacy constraints. The trade-off is that it requires more upfront design work, more change management effort, and typically a longer implementation timeline.
Brownfield: converting what you have
Brownfield is faster and less disruptive for organisations whose current ECC configuration is relatively clean and aligned with how they want to operate going forward. You retain historical data, existing integrations, and familiar processes. The risk is that you also carry forward any technical debt, outdated customisations, or process inefficiencies that were already present in ECC.
Many organisations end up with a hybrid approach, sometimes called a selective data transition, where they convert parts of the system and rebuild others. Choosing between these paths is one of the first decisions in any SAP transformation, and it has a direct impact on budget, timeline, and risk. We work with both greenfield and brownfield projects and help organisations make this decision based on their specific situation rather than a generic recommendation.
What are the biggest risks in an SAP 2027 transition?
The biggest risks in an SAP S/4HANA transition are data quality issues during migration, underestimating the cutover window, and low user adoption after go-live. These three factors are responsible for the majority of failed or delayed SAP transformations, and all three are manageable with the right preparation and expertise.
Data migration is consistently one of the highest-risk phases. Moving years of transactional and master data from ECC to S/4HANA requires thorough As-Is analysis, rigorous cleansing, and multiple rounds of testing before the actual migration runs. Errors discovered after go-live are far more expensive to fix than errors caught during preparation.
Cutover planning is another area where things go wrong. The cutover window, the period when you switch from the old system to the new one, is typically tight and leaves very little room for error. A poorly planned cutover can disrupt operations for days or weeks. Effective cutover management includes real-time monitoring, clear rollback procedures, and hypercare support in the days immediately after go-live.
User adoption is the risk that often gets underestimated until it is too late. A technically successful migration can still fail to deliver business value if employees do not understand or use the new system correctly. Change management that addresses behaviour, not just training, is what separates organisations that realise the benefits of S/4HANA from those that struggle for months after go-live.
When should an IT director start planning the SAP transition?
If you have not started planning your SAP S/4HANA transition yet, the time to begin is right now. With the 2027 deadline at the end of next year and realistic migration timelines ranging from 18 to 36 months, organisations beginning in 2026 are already working with a compressed schedule. The first step is not selecting a system integrator or building a project plan. It is getting an honest picture of where your organisation actually stands.
A maturity assessment gives you that baseline. It tells you how ready your processes, data, and organisation are for a transformation, and it surfaces the gaps that need to be addressed before a migration can realistically succeed. Without this starting point, organisations tend to commit budgets and timelines based on assumptions rather than facts, which is how projects run into trouble.
The organisations that navigate the SAP 2027 transition most successfully are the ones that start with clarity rather than urgency. That means understanding your current state, making a deliberate choice between greenfield and brownfield, and building a realistic roadmap before committing to a full programme. You can explore our full range of services to understand what a structured approach to SAP transformation looks like in practice.
How Optinus helps with your SAP 2027 transition
We support organisations at every stage of their SAP S/4HANA migration, from the first maturity assessment through to post-go-live hypercare. Our consultants have hands-on experience from real ERP migrations at leading multinationals, which means we bring practical knowledge to every phase of your programme, not just methodology.
- Maturity assessment: We give you a clear baseline of where your organisation stands before any budget or roadmap is committed.
- Program and project management: We coordinate your full transformation programme, aligning stakeholders, timelines, and workstreams across greenfield and brownfield projects.
- Data migration management: We use rigorous As-Is/To-Be analysis and testing procedures to protect data integrity throughout the migration.
- Cutover management: We plan and monitor your go-live window end-to-end, including hypercare and aftercare to keep operations running smoothly.
- Change management: We address both the technical and human side of transformation, driving genuine adoption across your organisation.
We work on-site and remotely, across the Netherlands, Belgium and internationally. If you want to understand where your organisation stands and what a realistic SAP transition looks like for your specific situation, get in touch with our team or learn more about what we do.
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