Eight Ways the Move from ECC to S/4HANA Goes Wrong, and How to Avoid Each One

SAP has committed to mainstream maintenance for Business Suite 7 core applications, the family that includes the SAP ERP Central Component, known as ECC, through the end of 2027. The clock is tighter than it looks and the process is full of pitfalls. Here is how to avoid the pitfalls.

Orpington Technologies | SAP S/4HANA Migration Insights SAP S/4HANA MIGRATION

SAP ECC to S/4HANA Migration: 8 Pitfalls
and How to Avoid Them

Most pitfalls in an SAP ECC to S/4HANA migration are visible months before they
cost anything. The projects that avoid them look early, decide deliberately and staff
for the work.

For any SAP ECC to S/4HANA migration, the date that matters is the end of 2027. SAP has committed to mainstream maintenance for Business Suite 7 core applications, the family
that includes the SAP ERP Central Component (ECC), through that date, with optional

extended maintenance through 2030 [1] . Extended maintenance carries a 2 percent premium [2] . The same survey of 198 senior leaders at German-speaking SAP customers found just 37 percent of ECC users wanting to be on S/4HANA by the end of 2027, and the report’s headline says about half are set to miss the date [2] . In the Americas, research by the SAP users’ group found 47 percent of 766 members already running S/4HANA or under way, with a further 22 percent planning to start within two years [3] . The clock is tighter than it looks. Panorama Consulting’s 2024 report puts the median ERP project at 15.5 months [4] . A project of that length started in November 2026 would end

around mid-February 2028, after mainstream maintenance has run out (Figure 1). That is an
illustration, since Panorama’s median covers ERP projects in general, but it explains why avoidable delay matters. The eight pitfalls below are the ones that add months, grouped by where they arise: in the plan, in the system and in the people.

Figure 1. The clock on ECC. Maintenance dates are from [1] , the extended-maintenance premium from [2] , and the project bar assumes the median 15.5-month ERP project from [4] starting in November 2026. The project bar is an illustration, not a forecast. © Orpington Technologies Inc. www.orpingtontech.com Page 1 of 7

Orpington Technologies | SAP S/4HANA Migration Insights Key takeaways The deadline. Mainstream maintenance for ECC runs to the end of 2027. Optional extended maintenance runs to 2030 at a 2 percent premium. The pattern. The eight pitfalls fall into three groups: the plan, the system and the people. The fix. Most pitfalls are visible early. A 90-day fact-finding phase built around SAP

Readiness Check, a custom code review, business partner cleansing and a skills map prevents the expensive surprises.

The safeguard. Have someone independent review the plan before money is committed. 1. Planning pitfalls: ownership, migration path and readiness Pitfall 1: Treating the S/4HANA migration as a technical upgrade

It is tempting to hand a conversion to the infrastructure team and wait. SAP’s own delivery
method, SAP Activate, runs through six phases that include requirements gathering, process

design, change management and data tools, not just the technical migration [5] . SAPinsider

makes the same point from the other side, arguing that brownfield is often mistaken for a purely technical move, when in fact the organization must still adopt mandatory changes

and use S/4HANA’s simplifications [6] . How to avoid it: name a business owner for each process area in the first phase, and give them decisions, not just updates. Pitfall 2: Choosing brownfield or greenfield by habit

Brownfield carries existing processes and data forward, greenfield builds a new system with
room for full process redesign, and selective data transition moves only chosen data and
leaves clutter behind. SAPinsider’s conclusion is that every S/4HANA journey is hybrid in

practice [6] . How to avoid it: make the choice area by area, using evidence from an assessment, and keep the decision open until that evidence exists. Table 1. Three S/4HANA migration approaches and the trade-off in each Approach What it does Trade-off Brownfield Carries existing processes and data into S/4HANA.

Mandatory changes and
simplifications still apply.

Greenfield Builds a new S/4HANA system and allows full process redesign.

More redesign effort in exchange for
a cleaner start.

Selective data
transition

Moves only chosen data and leaves
legacy clutter behind.

Configuration is data too, so it must
be chosen deliberately.

Pitfall 3: Meeting the simplification items late

One SAP Community author estimates that a typical system has about 50 to 80 relevant simplification items, some of which can be showstoppers, and advises running the check

early [7] . SAP Readiness Check covers simplification items, add-on and business function compatibility, sizing, interfaces such as business warehouse extractors, custom code and business partner synchronization [8] . How to avoid it: run Readiness Check, Maintenance

Planner and the simplification item check in the first weeks, while a surprise can still change
the scope.

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Orpington Technologies | SAP S/4HANA Migration Insights 2. System pitfalls: custom code and business partner data Pitfall 4: Carrying ECC custom code across unexamined

SAP benchmarks cited by SAPinsider put the share of ECC custom code that is unused or not compliant with S/4HANA standards at more than 50 percent. The same article reports that 77 percent of companies that remediated early cut cutover downtime by more than 40

percent [9] . Another SAP Community author warns that remediation can become a mini- project, and that not all custom code should move at all [7] . How to avoid it: pull usage data

first, retire what nobody runs, and sort the rest into fix now, rework in the sandbox and leave
behind.

Pitfall 5: Leaving customer and vendor data until last

A consultant writing on SAP’s news site calls customer-vendor integration “perhaps the most common ‘gotcha’ in SAP migrations” and notes that the migration cannot proceed

until it is complete [10] . In S/4HANA the business partner replaces the separate customer and vendor objects, and the business partner approach is the mandatory target; classic customer and vendor transactions are not available in the on-premise edition [11] . How to avoid it: audit and de-duplicate records early, treat the work as a business project with data owners, and rehearse the synchronization before the main conversion. Figure 2. Left: Americas’ SAP Users’ Group research, 766 members [3] ; SAP benchmarks on custom code reported by SAPinsider [9] ; and the German-speaking SAP user group survey of 198 leaders [2] . Right: typical simplification items [7] , median ERP project length [4] and the extended-maintenance premium [2] . 3. People pitfalls: skills, testing and deadlines Pitfall 6: Assuming the S/4HANA skills will be there In the Americas research, 48 percent of members said their organization lacked S/4HANA skills, and 29 percent named keeping knowledgeable staff a challenge [3] . A 2021 Gartner survey found 64 percent of information technology executives naming talent shortage as the biggest barrier to adopting emerging technologies [12] . How to avoid it: map the skills

each phase needs, hire for the permanent core and augment the rest. Deloitte’s 2024
Global Outsourcing Survey found 80 percent of executives planning to maintain or increase

their investment in third-party services [13] , and Orpington Technologies’ ERP staff augmentation exists for exactly this gap. © Orpington Technologies Inc. www.orpingtontech.com Page 3 of 7

Orpington Technologies | SAP S/4HANA Migration Insights Pitfall 7: Under-investing in testing and change management

Panorama’s 2024 report found fewer than half of organizations with an intense focus on
organizational change management, and resource constraints, staffing or budget, as the

most common cause of schedule overruns [4] . How to avoid it: test with real business data,

rehearse the cutover on a copy of production, and train users before go-live rather than
after.

Pitfall 8: Planning from the wrong end of the deadline Dates feel fixed, but they are choices with prices. Extended maintenance buys time at a 2 percent premium [2] . Starting late and hoping to compress the plan usually trades the premium for cutting corners on data, testing and training. How to avoid it: plan backward

from a realistic date, decide now whether extended maintenance is a strategy or a fallback,
and size the team to match.

Figure 3. A safer sequence for an ECC to S/4HANA conversion. Tools and focus areas are drawn from [7] , [8] , [9] and [10] ; the order is a typical practice, not a method SAP prescribes. Table 2. The eight S/4HANA migration pitfalls at a glance Pitfall Early warning sign How to avoid it 1. Technical upgrade No business owner named per process area Assign owners in the first phase 2. Path by habit Approach fixed before any assessment Decide area by area, on evidence

3. Late simplification
items

No Readiness Check results yet Run the checks in the first weeks 4. Custom code No usage data on custom programs Retire, fix now, rework or leave behind

5. Customer and vendor
data

Duplicates and no data owners Clean early; rehearse synchronization 6. Skills Key roles unfilled or single- threaded

Map skills by phase; augment the
peaks

7. Testing and change Training planned after go-live Real-data tests and cutover rehearsals 8. Deadline Plan built forward from today Plan backward from a realistic date 4. Your first 90 days of an ECC to S/4HANA migration

A sound S/4HANA migration plan starts with 90 days of fact-finding. Knowing the pitfalls is useful only if it changes what happens on Monday morning. The first 90 days decide
whether the eight pitfalls stay theoretical, and none of the steps below needs a signed
integrator contract.

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Orpington Technologies | SAP S/4HANA Migration Insights Days 1 to 30: establish the facts Run the SAP Readiness Check against the production system so that simplification items, add-on compatibility and custom code are counted rather than guessed [8] . Inventory

interfaces, reports and authorizations, and name a business owner for every process area. Agree in writing which of the three paths in Table 1 is being pursued and why, so the
decision survives a change of sponsor.

Days 31 to 60: clean and decide Start the custom code review and retire what nobody uses [9] . Begin business partner cleansing in the source system, where duplicates are cheapest to remove [11] . Compare the

skills the plan needs with the people available, and decide which gaps will be closed by training, by hiring and by borrowing credentialed practitioners.

Days 61 to 90: commit with evidence Build the timeline backward from a realistic cutover window and price extended maintenance as a deliberate option rather than a rescue [2] . Put test strategy, data

migration rehearsals and change management on the same plan as the technical work, and agree how progress will be reported to the steering group in plain language. An organization
that reaches day 90 with these in hand can negotiate with an integrator as an informed buyer.

Two habits keep the 90 days honest. First, every assumption in the plan gets an owner and
a date by which it will be proven or dropped. Second, someone who does not benefit from
the size of the project reviews the plan before money is committed. That second habit is
the one most often skipped, and it is the gap the next section addresses.

5. How Orpington Technologies supports your S/4HANA migration Know where you stand before you spend. Orpington’s Implementation Confidence Diagnostic is free, takes about 15 minutes with no sign-up, and returns a confidence score with the top three risk flags [14] . It is a low-cost first look for a team still deciding whether to start. Findings backed by evidence. The Full ERP Diagnostic Report checks every self-reported answer against real evidence, and a certified platform expert reviews the result. The scoring is built on Gartner research, and the assumptions behind it are disclosed [15] . Review by practitioners. Orpington describes a structure with no pyramid, so the people reviewing a client’s work are certified SAP practitioners rather than junior staff [15] . On an SAP conversion, that is the difference between a checklist and a judgment. A cost you know in advance. Pricing is a fixed fee per stage, with no day rates or retainers [15] . The cost of each decision is therefore known before it is made. Oversight from selection to hypercare. The Full ERP Implementation Partnership provides independent oversight from platform selection through hypercare [15] , and Orpington can

also lead the migration as the accountable delivery partner. Two further services cover
specific situations: Implementation Risk Remediation gives focused advisory sprints to close a known risk, and Stalled Implementation Recovery steps in when milestones slip or a
dispute with the integrator stalls the work.

Extra hands when you need them. Through ERP staff augmentation , three matched candidates arrive roughly four weeks after the engagement fee is confirmed. Every © Orpington Technologies Inc. www.orpingtontech.com Page 5 of 7

Orpington Technologies | SAP S/4HANA Migration Insights

candidate is credentialed by a certified practitioner, stays on Orpington’s payroll, works remotely and takes direction from the client’s project lead. A 90-day replacement guarantee covers the fit risk, and a single all-inclusive monthly invoice replaces payroll and

benefits administration [16] . Orpington’s own estimate puts the loaded cost of a direct hire at 1.25 to 1.4 times base salary.

For an organization facing the 2027 date, the sensible first step is the free diagnostic. If it confirms the plan is sound, it cost 15 minutes; if it finds a flag, the flag was found while it

could still be fixed [14] . 6. Frequently asked questions about ECC to S/4HANA migration When does SAP ECC mainstream maintenance end? SAP’s commitment to mainstream maintenance for ECC, part of Business Suite 7, runs through the end of 2027. Optional extended maintenance is available through 2030 [1] , at a 2 percent premium [2] . How long does an ECC to S/4HANA migration take? The median ERP project runs 15.5 months, according to Panorama Consulting’s 2024 report [4] . That figure covers ERP projects in general, so use it as a planning reference rather than a

forecast. Started in November 2026, a project of that length would finish around mid-
February 2028, after mainstream maintenance has ended.

What is the difference between brownfield, greenfield and selective data transition?

Brownfield converts the existing system and carries processes and data forward. Greenfield
builds a fresh S/4HANA system and allows full process redesign. Selective data transition
moves only chosen data and leaves legacy clutter behind. SAPinsider concludes that every

S/4HANA journey is hybrid in practice [6] , so decide area by area (see Table 1). How many simplification items should we expect? A typical system has about 50 to 80 relevant simplification items, according to one SAP Community author, and some can be showstoppers [7] . SAP Readiness Check reports on these items along with add-on compatibility, sizing, interfaces, custom code and business partner synchronization [8] , so run it in the first weeks of the project. Why do customer and vendor data have to move to business partners? In S/4HANA the business partner replaces the separate customer and vendor objects, and classic customer and vendor transactions are not available in the on-premise edition [11] . Auditing and de-duplicating records early makes the synchronization far easier to rehearse. What should we do first? Run SAP Readiness Check against the production system, name a business owner for every process area and agree in writing which migration path you are pursuing [8] . For a quick first look at your risk, Orpington’s free Implementation Confidence Diagnostic takes about 15 minutes [14] . Sources & Further Reading [1] LeverX – “SAP ECC End of Support 2027 UK: What UK Businesses Need to Do Now” [2] The Register – “Half of German-speaking SAP users set to blow past 2027 ECC support deadline,” February 2026 © Orpington Technologies Inc. www.orpingtontech.com Page 6 of 7

Orpington Technologies | SAP S/4HANA Migration Insights [3] The Register – “American SAP shops ramp up S/4HANA migrations” (report on research by the Americas’ SAP Users’ Group, 766 members), April 2024 [4] Panorama Consulting Group – “The 2024 ERP Report” [5] SAP Learning – “Describing the Deployment Process and the SAP Activate Methodology” [6] SAPinsider – “All SAP S/4HANA Journeys Are Hybrid,” February 2023 [7] SAP Community – “Tools to Support SAP S/4HANA Conversion Project,” Hafizur Rahman, July 2020 [8] SAP Community – “SAP Readiness Check 2.0: Insights and Flavors,” Paresh Shrivastava, May 2020 [9] SAPinsider – “How to Prepare SAP Custom Code for S/4HANA,” Bindiya Kour, February 2026 [10] SAP News Center – “The SAP Migration Mistake Most Companies Make,” Tracy Gore, October 2025 [11] SAP Community – “Business Partner Approach in SAP S/4HANA,” January 2018 [12] Gartner – “Gartner Survey Reveals Talent Shortages as Biggest Barrier to Emerging Technologies Adoption,” September 2021 [13] Deloitte – “Global Outsourcing Survey 2024” [14] Orpington Technologies – Implementation Confidence Diagnostic [15] Orpington Technologies – Services overview [16] Orpington Technologies – “ERP Staff Augmentation” © Orpington Technologies Inc. www.orpingtontech.com Page 7 of 7