Yes, a mid-sized company can complete an SAP S/4HANA migration before 2027, but only if the project starts now and moves without delay. SAP’s mainstream maintenance for ECC 6.0 ends in 2027, which makes this year a hard planning deadline for most organisations still running legacy SAP systems. The sections below cover the timeline realities, migration approaches, and risks you need to understand before committing to a roadmap.
What is the actual SAP S/4HANA migration deadline for mid-sized companies?
SAP has set 2027 as the end of mainstream maintenance for SAP ECC 6.0. After that date, standard support, patches, and updates will no longer be provided under a standard contract. For mid-sized companies still running ECC, this means 2027 is not a soft recommendation but a firm commercial boundary that affects system security, compliance, and operational stability.
It is worth noting that SAP offers extended support options at an additional cost, and some organisations may qualify for extended maintenance agreements. However, relying on those extensions as a strategy is expensive and delays the inevitable. The organisations that treat 2027 as a real deadline and start planning in 2026 are best positioned to migrate on their own terms rather than under pressure.
For mid-sized companies, the practical implication is straightforward: if your project has not started yet, the window to complete a well-managed SAP S/4HANA migration before the deadline is narrow. A rushed migration carries far more risk than a well-planned one, which is exactly why starting with a clear baseline matters so much right now.
How long does an SAP S/4HANA migration realistically take for a mid-sized company?
For a mid-sized company, a realistic SAP S/4HANA migration typically takes between 12 and 24 months from project initiation to go-live. The actual duration depends on the complexity of your current system landscape, the number of integrations, the volume and quality of your data, and the approach you choose.
Here is a rough breakdown of how a typical migration timeline looks:
- Months 1 to 3: Maturity assessment, scoping, and project setup
- Months 3 to 8: Design and configuration (blueprinting, process mapping, As-Is/To-Be analysis)
- Months 8 to 14: Build, data migration preparation, and integration testing
- Months 14 to 18: User acceptance testing, cutover planning, and change management
- Months 18 to 24: Go-live, hypercare, and post-go-live stabilisation
A company starting in mid-2026 with an 18-month timeline is cutting it close for a 2027 go-live. That is why the first step should not be a full project kickoff but a structured project management assessment that gives you an honest picture of your organisation’s readiness before the clock starts running.
What’s the difference between a greenfield and brownfield SAP S/4HANA migration?
A greenfield migration means building your SAP S/4HANA environment from scratch, without carrying over existing configurations, customisations, or historical data from your legacy system. A brownfield migration means converting your existing SAP ECC system directly into S/4HANA, preserving your current setup and data. The right choice depends on how much of your current SAP landscape is worth keeping.
Greenfield: starting fresh
Greenfield gives you the opportunity to redesign your business processes using SAP’s standard best practices. It is a stronger option if your current ECC system is heavily customised, outdated in its process design, or if you want to use the migration as a genuine business transformation rather than a technical upgrade. The trade-off is a longer implementation timeline and higher change management demands, because users are moving to an entirely new way of working.
Brownfield: converting what you have
Brownfield is faster and less disruptive because it converts your existing system rather than rebuilding it. It is a practical choice if your current processes are largely sound and you want to reach S/4HANA with minimal operational disruption. The risk is that you carry forward technical debt, outdated customisations, and data quality issues if these are not addressed during the migration. A thorough data migration management process is important here to avoid importing old problems into a new system.
Many mid-sized companies under time pressure lean toward brownfield because of the shorter timeline, but this only works well if the underlying data and processes are in reasonable shape. Reviewing our full range of services can help you understand what preparation each approach actually requires.
What are the biggest risks of rushing an SAP S/4HANA migration?
Rushing an SAP S/4HANA migration to meet the 2027 deadline introduces risks that can be more damaging than a delayed go-live. The most common failure points are poor data quality, inadequate testing, weak cutover planning, and low user adoption. Any one of these can cause serious operational disruption after go-live.
The risks break down into three main categories:
- Data integrity: Migrating dirty, incomplete, or poorly mapped data into S/4HANA creates problems that are difficult and expensive to fix post-go-live. Skipping rigorous As-Is/To-Be data analysis to save time is one of the most common and costly shortcuts.
- Cutover failure: The cutover window, the period when you switch from your old system to S/4HANA, is the highest-risk moment in the entire project. Without detailed cutover planning and real-time monitoring, even a well-prepared migration can go wrong at the last moment. End-to-end cutover management, including hypercare and aftercare, is what protects operational continuity when it matters most.
- Change fatigue and low adoption: A technically successful go-live can still fail if the people using the system are not ready. Rushing the change management workstream leads to resistance, workarounds, and a system that never delivers its intended value.
The answer to these risks is not to slow down indefinitely, but to plan more precisely. A maturity assessment at the start gives you an honest view of where the real risks sit in your specific organisation, so you can allocate time and resources where they matter most rather than spreading effort evenly across the project.
Should a mid-sized company start its SAP S/4HANA migration now?
Yes, a mid-sized company should start its SAP S/4HANA migration now. With the 2027 maintenance deadline approaching and realistic migration timelines running between 12 and 24 months, 2026 is the last point at which a properly managed migration can be completed in time. Starting now does not mean rushing. It means beginning with a structured assessment so the project is built on solid ground from day one.
The companies that struggle most with ERP migrations are not the ones that started too early. They are the ones that delayed the start, underestimated the complexity, or skipped foundational steps in favour of speed. A clear baseline, a realistic roadmap, and the right partner from the beginning make the difference between a migration that delivers value and one that creates disruption.
If your organisation is still on SAP ECC and has not yet defined a migration plan, the most useful action right now is to understand where you actually stand before committing to a timeline or budget.
How Optinus helps with your SAP S/4HANA migration
We work with mid-sized and enterprise organisations across the full SAP S/4HANA migration journey, from the first assessment through to post-go-live stabilisation. Here is what that looks like in practice:
- Maturity assessment: We start by giving you an honest baseline of your current processes, data quality, and organisational readiness. This creates clarity before any budget or roadmap is committed.
- Project and program management: Our consultants have hands-on experience from real ERP migrations at leading multinationals, not just methodology. We manage scope, timelines, and stakeholder expectations across every workstream.
- Data migration management: We use rigorous As-Is/To-Be analysis and testing procedures to protect data integrity throughout the migration, so you go live with clean, accurate data.
- Cutover management: We plan and monitor the cutover end-to-end, including hypercare and aftercare, to make sure the transition from your legacy system to S/4HANA does not disrupt daily operations.
- Change management: We address both the technical and human side of transformation, building genuine adoption across your organisation rather than just delivering training.
- Available on-site and remote: We work across the Netherlands, Belgium, and internationally, adapting to how your organisation operates.
If you want to understand where your organisation stands and what a realistic migration plan looks like, get in touch with our team or learn more about what we do.
