SAP S/4HANA Migration in 2027: Why 2026 Is the Decision Year

Dates don’t cause S/4HANA failure. Decision compression does.

With the 2027 SAP ECC support deadline approaching, the organizations that navigate S/4HANA migration well are the ones making better decisions now, not faster ones.

Every conversation about SAP S/4HANA migration starts the same way: “ECC support ends in 2027.” That statement is factually correct. It is also strategically incomplete.

After 200+ S/4HANA engagements, here is what we have learned: the date is not what breaks programs. What breaks them is what happens to organizations that wait until the date feels uncomfortably close, and then make consequential decisions under pressure rather than with clarity.

There is a name for this. It is called decision compression, and it is quietly reshaping the market right now.

When should a large enterprise begin its S/4HANA migration?

A full S/4HANA migration for a large enterprise typically requires 18 to 36 months. Organizations targeting a go-live before the 2027 SAP ECC support deadline need to be in active assessment by mid-2026 at the latest. Starting later does not create a worse migration: it eliminates the option of a well-planned one.

The market data makes this concrete

A 2025 Horváth study of 200 SAP user companies found that only 8% of organizations that have completed their S/4HANA migration did so on schedule, with projects taking an average of 30% longer than planned. In more than six out of ten cases, the planned budget was exceeded.

The root cause, according to the same research, is not technical failure. The leading reasons are scope expansion during transformation, a poorly managed data transition, a blueprint that gets revised rather than fixed, and a lack of clear governance. These are decision problems, and almost all of them trace back to choices made too quickly, too late, or without clarity about what was actually being decided.

A separate 2026 survey by Precisely and ASUG found that 30% of SAP migration projects are either delayed or over budget, and that is among organizations actively in motion. The ones still in evaluation face something more significant: a narrowing window in which the quality of their decision-making is about to matter most.

What decision compression actually looks like

Decision compression is not a single event. It is a gradual narrowing of options that organizations often do not notice until they are already inside it. It shows up in three consistent patterns.

None of these decisions feel like mistakes when they are made. They feel like pragmatism. The cost shows up later: in rework, in post-go-live disruption, and in the erosion of confidence in the program itself.

The window that matters is not 2027

2026 is the year that determines how 2027 unfolds for most large enterprises. As of early 2026, legacy SAP ECC use has fallen below 50% of organizations for the first time, but 35% of larger enterprises, those with the most complex landscapes, remain in the planning or exploration phases.

These are precisely the organizations for whom a rushed migration carries the highest risk, and for whom the readiness assessment window is narrowest. An organization that has not begun a structured assessment by mid-2026 is not choosing between a good migration and a rushed one. It is choosing between a rushed migration and an extended maintenance premium, while the talent pool it needed becomes unavailable.

The organizations that navigate this well are not necessarily the ones moving fastest. They treated 2026 as a decision window rather than a waiting room. They separated assessment from execution, made trade-offs consciously with an understanding of their actual landscape, and kept their leverage because they started before pressure forced their hand.

What good SAP S/4HANA migration planning looks like right now

The single highest-value action available to most enterprise SAP leaders in 2026 is not committing to a migration path. It is building the clarity that makes a commitment defensible.

None of this requires a commitment to execute. It requires a commitment to understand. The organizations that make it now, before the best delivery teams are booked and before scope decisions get made by default, are the ones that will look back at 2026 as the year they got ahead of this. The ones that don’t will be the ones saying, months into execution: we should have known this earlier.