SAP S/4HANA Migration: Greenfield or Brownfield?

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You only get one shot to get it right.
Choosing the wrong path to S/4HANA can cost millions, derail operations, and delay value for years.

But the bigger mistake? Delaying the decision while teams debate theory.

CEOs and CIOs across Europe, the Middle East, and the USA are under pressure to migrate – but the real risk isn’t when you move. It’s how you lead the migration on the ground.

So let’s break it down.

Why S/4HANA Projects Keep Failing

Whether you pick Greenfield or Brownfield, the core problems usually come later – and they’re rarely about technology.

What stalls most S/4HANA migrations?

KPIs are unclear and keep shifting mid-project
Business users never fully adopt the new workflows
Legacy data corrupts the entire reporting model
Vendor accountability blurs — and no one owns the delays
Internal teams are stretched thin across daily ops and transformation

The result? Projects drag 12–18 months over budget. Teams revert to spreadsheets. Confidence erodes.

At CE Interim, we’ve been called in to recover dozens of failing migrations – and in most cases, the choice between Greenfield and Brownfield wasn’t the real issue. Execution was.

Greenfield vs. Brownfield: What You Need to Know

Here’s a quick reality check on both approaches – without the marketing fluff.

Greenfield Migration

A fresh implementation of S/4HANA with redefined processes.

✅ Pros:

Clean slate, standardized processes
Ideal for companies with outdated or fragmented ERP systems
Opportunity to drive transformation, not just IT upgrade

⚠️ Risks:

Higher change management burden
Significant re-training and process redefinition
Can stall without strong adoption leadership

Brownfield Migration

A technical conversion from ECC to S/4HANA, preserving existing customizations.

✅ Pros:

Faster time-to-deploy in some cases
Keeps historical data and existing processes
Lower disruption to day-to-day ops (in theory)

⚠️ Risks:

Carries over legacy complexity
Limited process improvement
Hidden compliance and performance gaps remain

The Third Option: Hybrid — With the Right Leadership

In practice, most successful migrations are hybrid.
Some functions need full redesign (e.g., Finance, Supply Chain), others just need cleanup.

But here’s the catch: this only works if someone owns the delivery end-to-end. Not the vendor. Not internal IT. A real transformation leader.

What an Interim S/4HANA Leader Does in Week One

If your project’s already behind (or hasn’t started), the right interim executive can recover momentum fast:

In the first 5–7 days, an interim CIO or ERP Program Manager will:

I. Reset the mission.

Align board and operational teams on why the migration matters — and what “done” looks like.

II. Audit the real status.

Vendors, master data, user feedback, training, scope creep — all logged without blame.

III. Fix ownership gaps.

Define clear accountability across business, IT, external partners, and internal champions.

IV. Rebuild the roadmap.

Translate goals into measurable deliverables. Adjust timelines without masking reality.

V. Communicate like a leader.

Reset trust. Calm nerves. Replace technical jargon with operational clarity

Firms like CE Interim embed interim CIOs or S/4HANA leads within 72 hours — often during tense moments when failure is no longer an option.

What Happens After Week 1: From Stabilisation to Go-Live

A credible S/4HANA migration leader doesn’t stop at diagnosis. After the first week, the interim shifts into delivery gear:

By Week 2–3:

Launch daily/weekly routines to track real adoption
Cut redundant workstreams and refocus teams
Lead vendor meetings with renewed accountability
Establish early warning systems for scope or timeline creep

By Week 4–6:

User training intensified and tailored per function
Clean master data migration kicks off
Reporting dashboards align with exec KPIs
Resistance managed through real-world wins (e.g. faster approvals, better insights)

By Month 2–3:

Go-live prep rehearsed under pressure (mock scenarios, fail tests)
Business and IT work in sync — same language, same targets
CFO, COO, and site leads aligned on value realization

Firms like CE Interim embed interim ERP leaders who own this full arc – from fire-fighting to clean handover

Real-World Example: Greenfield Rescue in CEE

A European Tier-1 automotive supplier had chosen Greenfield.
But six months in, adoption lagged, and go-live was slipping quarter after quarter.

CE Interim installed a hands-on ERP Program Manager. Within four months:

Go-live executed successfully
90%+ user adoption achieved
Legacy workarounds retired permanently

The lesson? The path didn’t matter as much as the leadership did.

How You Know It’s Already Slipping

The warning signs often show up quietly.

Workarounds reappear as teams fall back on spreadsheets or old systems.
IT and business stop aligning, speaking in different terms and chasing separate goals.
Board updates become harder to produce–and even harder to trust.

Vendors begin steering decisions, while internal accountability weakens. And before long, 40% of the budget is gone without clear progress or value.

At that stage, recovery is still possible–but it’s slower, riskier, and costlier.
Interim leadership prevents this spiral by restoring control before things unravel.