Every enterprise S/4HANA migration follows a similar arc: it looks like a technology project in the planning room, then reveals itself as a business transformation the moment it touches custom code, data, and the systems surrounding the ERP core. The teams that come through it cleanly are rarely the ones with the most budget. They are the ones who found the complexity early, named the risks honestly, and built a plan around them. This guide walks through the six risks that most often derail enterprise migrations—and the practical ways we have seen leaders keep them contained.
- Why custom code remediation must start before selecting the technical migration path
- The difference between technical data transfer and business-ready data validation
- How to isolate critical peripheral systems (CRM, WMS, Banking) from cutover shocks
- Establishing a dual-track cutover rehearsal schedule with rollback triggers
Risk 1: Underestimating Custom Code
Legacy developments accumulate quietly over a decade or more. A report written for one manager, an interface added for one bank, a workaround that became a process—none of it looks like a problem until the migration team realizes that hundreds of custom objects now sit on the critical path.
The real cost is not the code itself. It is the uncertainty. You cannot build a credible migration plan until you know which developments create genuine business value, which are obsolete, and which will break against a simplified S/4HANA core.
Start by classifying custom code into what should be retained, remediated, redesigned, replaced, or retired. That single exercise turns a vague risk into a concrete, manageable workstream—and it should happen before you commit to a technical migration path, not after.
- Inventory every custom object and dependency before selecting a migration approach
- Separate business-critical development from obsolete technical debt
- Plan remediation for code that must survive, and retirement for code that should not
Preserve what creates business value. Simplify what creates unnecessary complexity. Modernize what needs to evolve.
Risk 2: Treating Data as a Technical Task
Data migration is one of the most underestimated parts of an ERP transition. The challenge is rarely “can we move the records.” It is determining what should move, what should stay behind, what needs cleansing, how values should be mapped, and how migrated data will be validated against business expectations.
When data quality is treated as an IT exercise, the problems surface after go-live—as reconciliation delays, reporting errors, and a slow erosion of business confidence in the new system.
Connect data decisions to business requirements. Define the data scope, clean the source, map it to target structures, execute in controlled phases, validate against real scenarios, and get explicit sign-off from the business owners who depend on the information.
- Define what must move and what can be archived or left behind
- Cleanse duplicates, incomplete records, and inconsistent values before migration
- Validate migrated data against business expectations—not just technical reconciliation
The right question is not “can we move the data?” but “what data should move, in what form, and how will we prove it is correct?”
Risk 3: Missing Integration Dependencies
An S/4HANA migration changes interfaces—even when a business process appears unchanged. Underlying technical endpoints, data structures, APIs, middleware, and connection mechanisms all shift during the transition.
The ERP may be changing, but the systems connected to it still have to work: CRM, e-commerce, legacy applications, data platforms, banking interfaces, warehouse and manufacturing systems, and every third-party application in between.
Map the integration ecosystem before migration begins. Every connection is a potential dependency during transformation, and the ones outside the SAP team’s direct control are the ones most likely to become critical-path surprises.
- Inventory all SAP interfaces, APIs, middleware, EDI, and connected applications
- Identify which integrations are business-critical and test them end-to-end
- Plan integration redesign early rather than discovering broken flows at cutover
Your S/4HANA program does not end at the SAP boundary. The systems around the core are part of the migration.
Risk 4: Testing Too Late
Testing is where migration risk becomes visible—and it is usually discovered later than it should be. When testing is compressed into the final weeks, process and integration issues surface inside the go-live window, when options are fewest.
Testing should reflect how the enterprise actually operates: unit and integration testing, end-to-end process flows, data validation, interface testing, custom development, user acceptance, regression, and cutover readiness.
The goal is to reduce surprises between technical completion and business acceptance. Build testing into the migration plan from the beginning, with dry-run rehearsals that treat cutover as a repeatable drill rather than a one-time event.
- Include business users early so acceptance reflects real operating conditions
- Rehearse cutover in sandbox environments before the real window
- Test the business, not just the technology
The real test is whether the business still works—not whether the system boots.
Risk 5: Choosing the Wrong Migration Approach
SAP describes three major transition paths—system conversion, new implementation, and selective data transition. None is inherently right. The correct choice depends on your starting landscape, how much process change the business wants, data requirements, and the target architecture.
The wrong strategy increases both cost and complexity. A conversion preserves history but may carry forward legacy constraints. A greenfield implementation cleans the slate but demands more change. A selective transition offers a middle path when the landscape is complex or historical data requirements are specific.
Compare transition options against your actual starting point and transformation objectives—not against a preferred vendor narrative. A structured assessment is the difference between choosing a path and guessing at one.
- Assess the current landscape before comparing transition approaches
- Match the approach to business-process change appetite and data requirements
- Involve enterprise architecture early so the choice aligns with the target state
Risk 6: Focusing Only on Go-Live
An SAP migration is not finished because production is running. The weeks after cutover—stabilization, support, monitoring, performance tuning, and business user adoption—determine whether the transition is remembered as a success or a disruption.
Enterprises that treat go-live as the finish line often discover the opposite: the risk is simply deferred to the post-go-live period, where it is harder to manage and more visible to the business.
Include stabilization, hypercare, monitoring, and optimization in the program from the start. Define what steady state looks like before you begin, so the team knows what “done” actually means.
- Plan hypercare and post-go-live support before cutover, not after
- Define operational SLAs, monitoring, and escalation paths for steady state
- Treat optimization as an ongoing commitment, not an afterthought
A migration should leave the business better positioned—more efficient, more visible, more resilient—not simply running on a newer version.
S/4HANA migration risk is rarely a single event. It is a chain of small uncertainties—code, data, interfaces, testing, approach, and operations—that compound over the life of a program. The enterprises that succeed are the ones that surface those uncertainties early and give each one a clear owner, a clear plan, and a clear test. If you are planning a migration, start with the landscape you actually have, not the one you assume. That is where every realistic migration plan begins.