SAP S/4HANA Migration: The 2027 Deadline

⏰ What you need to know

SAP ends mainstream support for SAP ECC 6.0 in December 2027
Loss of security support, regulatory updates and compatibility with SAP Business AI (Joule)
The HANA in-memory database speeds up analytical processing by 100x and shrinks the database by 40 to 70%
On average, 30-40% of custom SAP ECC code is obsolete — a pre-migration audit can save 3-6 months of project time

Why migrate now — not in six months

The move to SAP S/4HANA is the biggest ERP programme of the decade. For organisations running SAP ECC — banks, manufacturers, distributors, public administrations — it is both a risk and an opportunity for deep transformation.

Beyond the end of support, S/4HANA brings measurable operational gains. The simplified data model removes dozens of intermediate tables and custom programs. Finance, Supply Chain and Manufacturing processes are native and integrated. Above all: SAP's built-in AI (Joule, SAP Business AI) only works with S/4HANA. Delaying the migration means going without the capabilities your competitors are already deploying.

Three migration approaches: strengths and limits

🔧 Brownfield

A technical conversion of the existing system in place. Keeps historical data and customisations.

6-12 months Moderate cost

If: little custom code, a stable system

🏗️ Greenfield

A new system from scratch. A complete redesign of business processes using S/4HANA best practices.

12-24 months High cost

If: deep transformation is needed

🎯 SDT (Selective Data)

A clean system with selective migration of critical data. The best of both worlds.

9-18 months Mid-range cost

Our recommendation

The Selective Data Transition (SDT) is emerging as the preferred approach for many organisations. It clears out the technical debt built up over 10-15 years of ECC while preserving mandatory regulatory data (accounting entries, transaction history). It is a smart compromise between the rigour of greenfield and the pragmatism of brownfield.

The five pitfalls that make migrations fail

Underestimating the clean-up of customisations. On average, 30-40% of custom SAP ECC code is obsolete or redundant. A pre-migration code audit (SAP Custom Code Migration Worklist) can save 3 to 6 months of project time and a significant share of the budget.
Ignoring change management. Key users must be involved from the design phase, not just during testing. SAP projects that fail are rarely technical failures — they are adoption failures.
Neglecting HANA sizing. An undersized in-memory database leads to poor performance from go-live. Sizing must be based on real data, not on vendor estimates.
Postponing the cloud strategy. S/4HANA runs on-premise, in a private cloud or in the public cloud (RISE with SAP). The infrastructure choice affects the 5-year TCO — this decision must be made before design, not after.
Planning without a buffer. SAP migrations routinely overrun their initial timelines by 20-30%. Building this reality into the plan rather than suffering it is a sign of project maturity.

An S/4HANA migration is not an IT project — it is a transformation programme that touches business processes, the organisation and company culture. Successful projects are sponsored at executive-committee level and have a dedicated change-management budget (15-20% of the total budget).

Recommended roadmap — 18 months

Phase 1 — Discovery (months 1-3): Audit of the current system, mapping of customisations, analysis of the data to migrate. Choice of strategy (brownfield, greenfield or SDT) and hosting model.

Phase 2 — Prepare (months 4-6): Custom code clean-up, S/4HANA sandbox, training of key teams. HANA sizing validated on real data.

Phase 3 — Realize (months 7-14): Configuration, development of adaptations, data migration, integration testing. UAT cycles with key users.

Phase 4 — Deploy (months 15-18): Cutover, go-live, hypercare. System stabilisation over 3 months with enhanced support.

SAP S/4HANA Migration: The 2027 Deadline, Strategy and Pitfalls to Avoid