ERP implementations fail in slow motion. The software goes live; the business does not. Orders stall, inventory lies, and everyone keeps a shadow spreadsheet “just until things settle.” A 12-month playbook will not make a global template easy, but it will stop you from pretending a four-month miracle is a plan.
Months 1–2: freeze scope and name owners
Write the operating model first: legal entities, inventory valuation, revenue recognition, and who is allowed to create items and customers. If those decisions slip into build, every workshop becomes a debate club. Appoint process owners with calendar time—not figureheads.
- RACI for order-to-cash, procure-to-pay, record-to-report, hire-to-retire
- Integration inventory (CRM, WMS, e-commerce, payroll, tax)
- Chart of accounts design principles
- Definition of done for data migration (not “we’ll cleanse later”)
Months 3–5: design with real transactions
Conference-room pilots should replay last Tuesday’s ugly order—not the happy path in the vendor script. Capture gaps as configuration, extension, or process change. If everything is an extension, you bought the wrong product or refused to change.
Suggested 12-month backbone
| Window | Focus | Exit criteria |
|---|---|---|
| M1–2 | Scope, owners, CoA, data rules | Signed RACI + integration list |
| M3–5 | To-be design + CRP | Decision log for top 50 gaps |
| M6–8 | Build, migrate v1–v2, integrations | Automated test pack on golden data |
| M9–10 | UAT, training, cutover rehearsal | Exit criteria met, no Sev-1 defects |
| M11 | Cutover + hypercare | Close first week in the new ERP |
| M12 | Stabilize + decommission | Shadow systems scheduled off |
Months 6–8: data is the critical path
Run at least three migration cycles. Reconcile AR, AP, on-hand, and open POs to the penny. Item duplicates will haunt ATP forever if you “merge later.” Assign a data steward per domain with authority to reject dirty loads.
Months 9–12: rehearse the business, not just IT
- UAT with the people who will work Saturday after go-live.
- A full cutover dress rehearsal including print, tax, and payment files.
- A hypercare bridge with floor walkers and a 15-minute stand-up.
- A date to turn off the old system’s create rights—read-only is not optional.
Conclusion
A realistic ERP year is mostly politics, data, and rehearsal. Software configuration is the middle third. Sequence owners before workflows, data before dashboards, and hypercare before the victory email. That is how a 12-month program becomes an operating company—not a lingering implementation.