Should you migrate to SAP S/4HANA before the 2027 deadline?

If you’re running SAP ECC today, you should plan to migrate to SAP S/4HANA before the 2027 mainstream maintenance deadline — but the right timing depends on your organisation’s complexity, readiness, and risk tolerance. Waiting is not automatically the safer option. Extended maintenance is available beyond 2027, but it comes at a cost and limits your access to new functionality. Below, we answer the questions that matter most when you’re weighing up this decision.

What happens to SAP ECC after the 2027 deadline?

SAP’s mainstream maintenance for ECC ends on 31 December 2027. After that date, SAP will no longer provide standard support, security patches, or legal and regulatory updates for ECC systems as part of a standard maintenance contract. Organisations still running ECC after 2027 will need to purchase extended maintenance, which SAP currently offers through 2030, at a significant additional cost.

Running on extended maintenance means you stay operational, but you’re essentially in a holding pattern. You won’t benefit from SAP S/4HANA’s embedded analytics, simplified data model, or the continuous innovation SAP is directing towards its flagship platform. Security vulnerabilities become a growing concern without regular patches, and regulatory compliance updates — tax law changes, reporting requirements — become harder to manage.

The 2027 deadline is also creating real resource pressure in the market. Experienced SAP consultants, system integrators, and implementation partners are already becoming harder to book as more organisations accelerate their migrations. Waiting until 2026 or 2027 to start a migration means competing for a shrinking pool of available expertise.

What’s the difference between a greenfield and brownfield SAP S/4HANA migration?

A greenfield migration means starting fresh — you implement SAP S/4HANA as a new system, redesigning your business processes from the ground up. A brownfield migration means converting your existing ECC system directly to S/4HANA, carrying over your current configuration, data, and customisations. The right approach depends on how much your organisation wants to change versus preserve.

Greenfield: clean slate, higher transformation effort

Greenfield gives you the opportunity to adopt SAP’s standard best-practice processes and shed years of accumulated customisations. It typically delivers more long-term value but requires significantly more time, budget, and change management effort. Your teams need to learn new processes, not just a new system. This approach suits organisations that want to modernise their operations fundamentally, not just lift and shift their current state into a new technical environment.

Brownfield: faster, but carries legacy complexity

Brownfield conversions are generally faster and less disruptive because you’re not redesigning processes from scratch. However, you carry forward your existing customisations, which can limit how much you benefit from S/4HANA’s simplified architecture. Organisations with heavily customised ECC systems often find that a brownfield conversion still requires significant remediation work to resolve compatibility issues.

We work with organisations on both approaches as part of our program management service, and the choice between greenfield and brownfield is one of the first strategic decisions we help clients work through — often starting with a maturity assessment to understand what the current ECC landscape actually looks like before committing to a path.

How long does an SAP S/4HANA migration actually take?

Most SAP S/4HANA migrations for mid-to-large enterprises take between 18 and 36 months from initial scoping to go-live. Smaller organisations with less complexity can complete migrations in 12 to 18 months. The timeline depends on the scope of process change, data quality, the number of integrations, and whether you’re running a greenfield or brownfield approach.

The phases that most often cause delays are data migration and testing. Data migration requires thorough cleansing, mapping, and validation before anything goes live. Testing — particularly integration testing and user acceptance testing — tends to be underestimated in early project plans. Cutover planning, the final switch from legacy to new system, also demands detailed preparation to avoid operational disruption.

If you’re starting in 2026, a realistic migration to S/4HANA before the end of 2027 is achievable for organisations with moderate complexity, but it requires starting now and moving quickly through the design and scoping phases. For more complex, multinational environments, the window is tight and the case for extended maintenance becomes more relevant as a bridging strategy.

Should you migrate before 2027 or wait for extended maintenance?

Migrating before 2027 is the right choice for most organisations that have the internal readiness and budget to do so. Extended maintenance is a valid short-term option for organisations that genuinely need more time, but it should be treated as a bridge, not a destination. The additional cost of extended maintenance, combined with the growing scarcity of available implementation resources, makes prolonged delay increasingly expensive.

The organisations best positioned to migrate before 2027 are those that started planning in 2024 or 2025, have strong executive sponsorship, and have already assessed their current ERP maturity. If you haven’t done that groundwork yet, rushing into a migration to hit an arbitrary deadline can create more risk than a structured 12-month delay with proper preparation.

The organisations for whom waiting makes more sense are typically those mid-way through other major business changes — mergers, restructuring, or large-scale operational shifts — where adding an ERP migration to the mix creates unacceptable risk to continuity. In those cases, a clear plan to migrate by 2029 or 2030 under extended maintenance, with preparation starting now, is a more responsible approach than a rushed go-live.

What are the biggest risks in an SAP S/4HANA migration?

The biggest risks in an SAP S/4HANA migration are poor data quality, underestimated change management, and cutover failure. These three areas account for the majority of project overruns, delayed go-lives, and post-go-live operational disruptions. Understanding them upfront helps you build mitigation into your programme from day one.

Data quality is consistently the most underestimated risk. Migrating dirty, incomplete, or poorly structured data from ECC into S/4HANA doesn’t clean the data — it just moves the problem. Rigorous As-Is analysis of your current data structures, combined with thorough testing before cutover, is the only reliable way to protect data integrity during the transition. You can explore our full range of services to see how data migration management fits within a broader programme approach.

Change management is frequently treated as a training exercise rather than a genuine programme workstream. The technical go-live can be flawless, but if your people don’t understand the new processes or resist adopting them, the business case for the migration quickly unravels. Effective change management starts well before go-live and continues into the post-live period.

Cutover risk is the moment everything becomes real. The cutover window — the period when your old system goes offline and the new one goes live — is where years of planning either hold together or fall apart. Detailed cutover planning, real-time monitoring during the transition, and a structured hypercare period immediately after go-live are what separate smooth transitions from operational crises.

How Optinus helps with SAP S/4HANA migration

We support organisations through every phase of an SAP S/4HANA migration, from the first strategic questions through to post-go-live stability. Here’s what that looks like in practice:

Maturity assessment — before any budget is committed or roadmap is agreed, we give you a clear baseline of where your organisation actually stands in terms of processes, people, and systems
Greenfield and brownfield programme management — we coordinate workstreams, stakeholders, and timelines across the full programme, available both on-site and remotely across the Netherlands, Belgium, and internationally
Data migration management — we run rigorous As-Is/To-Be analysis and testing procedures to prevent data loss and errors during the migration
Cutover management — we manage the cutover end-to-end, including real-time monitoring and a structured hypercare period, so operational continuity is never at risk
Change management — we work on both the technical and human side of transformation, driving genuine adoption across your organisation rather than just delivering training sessions

We cover the full spectrum from project manager to business architect, with consultants who have done this on the ground at leading multinationals — not just built frameworks about it. If you’re working through the 2027 decision right now, get in touch with our team or learn more about what we do to see how we can help you move forward with clarity.

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