SAP ECC mainstream support ends Dec 31, 2027. Your migration window is closing. Complete this 15-point pre-migration checklist to assess risk, identify hidden complexity, and build a realistic migration roadmap.
By SAVIC SAP Practice · ERP Migration Team · Jul 13, 2026 · 24 min read
The Migration Reality: Why 40% of SAP Projects Exceed Timeline
SAP ECC to S/4HANA migration is the most complex enterprise transformation most companies will execute. According to industry research, 40% of S/4HANA migrations run 6–12 months over schedule, and 35% exceed budget by 20%+. SAVIC has executed 50+ ECC migrations. The ones that stayed on time and budget had one thing in common: a comprehensive pre-migration checklist completed before design phase was finalized.
The Pre-Migration Checklist — 15 Critical Questions Before You Start
Section 1: Business Strategy & Scope (Weeks 1–4)
✓ 1. Have you confirmed the 2027 ECC end-of-support deadline?
SAP ECC mainstream support ends December 31, 2027. This is not a rumor — SAP has confirmed it multiple times. Extended support costs 3x normal license fees. Get written CFO confirmation that you understand the financial implications.
✓ 2. Have you defined which business units are in scope for Phase 1?
Create a scope matrix: Business units, ECC instance count, User headcount, Annual transaction volume, In-scope (Yes/No). Phase 1 should include no more than 60% of your enterprise.
✓ 3. Have you completed Greenfield vs. Brownfield decision with CFO + CIO approval?
Greenfield: 9–15 months, $3M–$8M, redesign processes. Brownfield: 15–24 months, $5M–$12M, migrate legacy code. This decision determines your entire timeline and budget. Get written sign-off.
Section 2: Enterprise Architecture & Technical Landscape (Weeks 4–8)
✓ 4. Have you completed a full inventory of your SAP landscape?
Common discovery: enterprises think they have 2 ECC instances but actually have 5. Create an SAP landscape map with instance names, versions, business units, user counts, and customization debt.
✓ 5. Have you mapped all integrations with non-SAP systems?
Most ECC landscapes have 20–40 integration touch points. Each must be redesigned for S/4HANA. SAVIC clients with 30+ integrations typically add 4–8 weeks to their timeline.
✓ 6. Have you assessed your custom code?
SAP provides a "simplification list" identifying which ECC functions are being retired. Run SAP Code Inspector and create a custom code assessment. Budget rule: > 50,000 lines of custom ABAP = 8–12 weeks, $200K–$500K.
✓ 7. Do you have a cloud vs. on-premise deployment decision?
S/4HANA Cloud = 40% cheaper TCO, automatic updates. On-Premise = customization flexibility. If you cannot clearly state your deployment choice, you are not ready for design phase.
Section 3: Data Quality & Governance (Weeks 8–16)
This is where migrations succeed or fail. Data quality is the #1 cause of post-go-live problems.
✓ 8. Have you performed a data audit of your master data?
S/4HANA has a simplified, optimized data model. It does not tolerate inconsistencies that ECC allowed. Conduct pre-audit of top 500 customers, 500 vendors, 500 GL accounts, 1000 products. Target: 95%+ complete, 99%+ accurate, 100% compliant.
✓ 9. Have you identified and scrubbed duplicate records?
Vendors may exist as 50 different records due to naming variations. Use a master data management tool to identify and merge duplicates. Budget: 3–6 weeks, $50K–$150K.
✓ 10. Do you have a data migration strategy with reconciliation rules?
Create a data migration runbook with: Extraction queries, Field mapping, Transformation rules, Reconciliation queries, Cutover sign-off criteria.
Section 4: Custom Code & Integration Readiness (Weeks 12–20)
✓ 11. Have you completed custom code remediation assessment?
For each Z-object touching a simplified function: Quantify business impact, Estimate remediation effort, Decide (remediate, replace, eliminate), Assign ownership, Set timeline.
✓ 12. Have you validated your integration suite choice?
For each integration: Is there a pre-built connector? If not, third-party connector? If not, custom development needed? This determines timeline and cost.
Section 5: Organizational Change & Training (Weeks 16–24)
✓ 13. Have you established a change management office (CMO)?
Without change management, adoption is 50–60%. With it, you get 80%+ by month two. Establish: Steering Committee, PMO, CMO, Functional Workstreams.
✓ 14. Have you designed role-based training?
Generic training fails. Create a training matrix: Business role, Key processes, How they change, Training topics, Estimated time per user.
✓ 15. Do you have a post-go-live support plan with 24/7 support?
The first 72 hours post-go-live are mission-critical. Create a hypercare support plan with primary team, escalation path, SLAs, and weekend coverage — many enterprises hand this over to SAP Basis administration services for ongoing monitoring once hypercare ends.
The Pre-Migration Risk Assessment
Green Risk (< 6 months, < $5M): Greenfield, < 500 users, < 10 integrations, < 10,000 lines of custom code, clean master data.
Yellow Risk (6–12 months, $5M–$8M): Brownfield, 500–2,000 users, 10–25 integrations, 10,000–50,000 lines of custom code, 15–25% master data quality issues.
Red Risk (> 12 months, > $8M): Complex brownfield, > 2,000 users, > 25 integrations, > 50,000 lines of custom code.
If your migration is Red Risk, do not proceed without adding 4–6 months to your timeline and $2M–$4M to your budget.
Your Next Step
If you are 12–24 months away from your ECC 2027 deadline, now is the time to execute this checklist. SAVIC can complete this assessment in 8–12 weeks. Know More →
Last reviewed: Jul 13, 2026 by SAVIC SAP Practice
Frequently Asked Questions
How long does an ECC to S/4HANA migration checklist assessment take?
The 15-point checklist typically takes 6–12 weeks to complete, depending on your landscape complexity. For greenfield migrations with simple landscapes, expect 6–8 weeks. For brownfield migrations with complex landscapes, expect 10–12 weeks. This upfront investment prevents 8–12 weeks of delays later.
What is the difference between data migration and data transformation?
Data migration is moving data from point A to point B. Data transformation is changing data format/structure along the way. In ECC→S/4HANA, transformation is essential because the two systems have different data models.
What are the biggest risks in ECC to S/4HANA migration?
Top risks: (1) Underestimating custom code remediation, (2) Master data quality issues, (3) Integration redesign complexity, (4) Organizational change management failure, (5) Post-go-live performance tuning needs.
Should we choose greenfield or brownfield, and how do we decide?
Choose greenfield if your ECC landscape is heavily customized and you're willing to reengineer processes. Choose brownfield if you have mission-critical custom code or an aggressive timeline.
How much does the pre-migration assessment cost?
A comprehensive assessment covering all 15 checklist items costs $150K–$300K depending on landscape complexity. This investment typically pays for itself by preventing a 6-month project delay.
Can we migrate data while ECC is still running (zero-cutover migration)?
No. S/4HANA must be cut over in a specific window because the two systems cannot coexist in a transactional state. You can run ECC in read-only mode post-cutover for archive/historical reporting.
What is our SAP license cost after migration to S/4HANA Cloud?
S/4HANA Cloud licensing is typically 10–20% lower than ECC licensing because cloud includes more functionality out-of-box. However, total cost of ownership is 30–40% lower because you eliminate infrastructure overhead.
