The SAP ECC Deadline Is Real: Why 2027 Should Set Your Migration Timeline

By Gartner's count, only about 39% of SAP's roughly 35,000 ECC customers, call it 14,000 organizations, had actually migrated to S/4HANA by the end of 2024. Independent estimates from IDC and Forrester both put the share still expected to be running ECC beyond 2027 north of 40%. Basis Technologies' own modeling puts completion by the 2027 deadline at only 57% of the base, with the rest of the installed base not fully migrated until the mid-2030s.

of SAP's ECC installed base is projected to still be running legacy ERP when mainstream maintenance ends in 2027: roughly 17,000 organizations, by Gartner's estimate.

The stall isn't purely inertia or budget cycles. Much of it comes down to what organizations have watched happen to the peers who went first. A 2025 study by the consultancy Horváth, covering 200 companies with at least €200 million in annual revenue across the DACH region, Northern and Eastern Europe, and the US, found that S/4HANA transformations take 30% longer than planned on average. Fewer than 10% of projects finish without exceeding their original timeline.

The same study found that 65% of organizations experienced significant budget deviations, and 65% reported strong-to-very-strong quality deficits in what they ultimately received. More than 60% of companies missed on budget, schedule, and result quality all at once. One bad vendor or an under-resourced IT team doesn't explain numbers like that. It points to a structural pattern across a large, well-funded sample of enterprise transformations.