The Clock Is Already Running.

31 December 2027. That is the date SAP has confirmed as the end of mainstream maintenance for SAP ECC. No further extensions. No reprieve. After that date, organisations running ECC will be on unsupported software, with no new security patches, no regulatory updates, and no fixes unless they pay a significant premium for extended maintenance.

Across Germany, Switzerland, and Austria, a survey conducted between December 2025 and January 2026 by the German-speaking SAP user group DSAG found that only 37% of ECC users plan to complete their S/4HANA migration by the end of 2027. Almost half of the rest intend to continue into 2030, relying on extended support, and 4% are targeting 2033. That is a financially and operationally costly decision. It is also one that many organisations are making not out of strategic choice, but because the scale of the migration work is only becoming clear now.

As of end-2024, less than 40% of SAP ECC customers had licensed SAP S/4HANA, according to Gartner. That means more than 60% of the global SAP installed base has not yet moved.

The window is closing

A full ECC to S/4HANA migration for a complex enterprise typically takes between 18 and 36 months. Organisations with multi-country deployments, significant custom code, or heavily integrated landscapes sit at the longer end of that range. An organisation that has not yet started a migration programme today, in mid-2026, will not complete by December 2027. The arithmetic is straightforward.

The financial calculus compounds the urgency. SAP's extended maintenance option through 2030 is available, but only after purchasing an S/4HANA licence and committing to a migration plan. The premium on top of standard maintenance fees represents significant additional cost for large ECC landscapes, with no new capabilities in return. Every month of delay is a month of dual cost and diminishing options.

Beyond cost, there is a capacity problem in the market. As the 2027 deadline approaches and the urgency of the remaining 60% of ECC customers becomes undeniable, demand for qualified S/4HANA migration resources is tightening. Day rates for available consultants are rising. Lead times to assemble experienced teams are lengthening. Organisations engaging implementation partners in late 2026 will find compressed programme timelines that increase delivery risk.

Where migrations fail: the integration layer

Most organisations framing their S/4HANA transition as an ERP project are correct. But they are missing the harder problem. ERP migrations fail at the integration layer. Almost every production ECC system has been extended over years or decades with custom interfaces, third-party connectors, EDI pipelines, legacy middleware, and bespoke integrations that were never documented and have never been tested at scale.

When the ERP changes, everything connected to it must be assessed, retested, and often rebuilt. The CRM that pulls customer data from ECC needs to speak to S/4HANA. The warehouse management system. The reporting platform. The external partner portals. The regulatory reporting feeds. Each of these represents an integration dependency that the ERP migration programme must account for, plan around, and either migrate or replace.

The integration challenges that most commonly derail ECC migration programmes include:

• Custom ABAP interfaces that connect ECC to third-party systems and have no equivalent in S/4HANA's standard stack
• Legacy middleware platforms reaching their own end of support on timelines that overlap with the ECC deadline
• Undocumented point-to-point integrations that only surface when test migrations fail in unexpected ways
• EDI pipelines connecting Swiss logistics and manufacturing operations to EU trading partners that must continue operating without interruption

A survey by Horvath found that almost 60% of companies that completed S/4HANA transformations ended up exceeding their planned schedule. The scope expansion and project management challenges that drive that number are, in most cases, rooted in integration complexity that was underestimated at the outset.

The Swiss context

Swiss companies face all the generic challenges of an ECC migration, and several that are specific to operating outside the EU. SAP localisation for Swiss payroll, Swiss VAT reporting under the domestic MWSTG, and the customs integration requirements for cross-border trade under the Bilateral Agreements all require careful validation in any S/4HANA migration.

Many Swiss manufacturing companies run ECC as the backbone of supply chains that cross the border into Germany, France, Austria, and Italy multiple times per week. The integration between their ECC landscape and their EU trading partners is not a peripheral concern. It is the operational core. Migrating the ERP while maintaining the reliability of those supply chain integrations is the central engineering challenge of the programme.

What needs to happen now

The organisations best positioned for a 2027 completion are the ones that have already mapped their integration landscape, identified the dependencies that will require rework, and aligned their migration programme accordingly. For everyone else, that mapping work needs to start immediately. Not as a future workstream. Now.

That work begins with an honest inventory: every system connected to ECC, every integration pattern in use, every custom interface that has accumulated over the lifetime of the installation. From that inventory, a realistic migration scope emerges. And from that scope, a realistic programme plan.

At Ampleshift, we specialise in exactly this complexity. We have helped organisations assess, rationalise, and rebuild integration landscapes in the context of large-scale ERP transformations. We bring senior integration expertise from day one, with AI-powered delivery that compresses assessment and build timelines without cutting corners. If the 2027 deadline is real to your organisation, the conversation starts here.