The cutover window hour by hour — freeze, final extract, load, reconcile, verify, open — the four-corner reconciliation across trial balance, subledger control accounts, open-document counts and master-data counts, the go/no-go decision points, the rollback plan, day-one readiness, the hypercare model through to exit, and what happens to the Epicor system afterwards.
Chapters 1 and 2 built the programme and the engine. This chapter is about the event that either validates or exposes both: the freeze, the load, the reconciliation, the go/no-go decision, and the weeks of hypercare that follow before anyone can honestly say the cutover worked.
The cutover window executes the full wave set (W1–W8) against a frozen Epicor snapshot plus a final delta. Window length is set per engagement — it is not a fixed commitment. A well-tuned engine processing a medium-sized Epicor estate targets 8–16 hours for W1–W7, plus delta and reconciliation time.
Four separate reconciliations — each comparing a named Epicor source to a named D365 report — must close before go-live. "Close" means an explicit, signed variance of zero (or an explained, approved rounding tolerance) for every corner, by every company in scope.
If any checkpoint fails, the default action is abort and remain on Epicor. Epicor is still the system of record until the read-only freeze is applied; aborting before that point has no lasting consequence beyond the rescheduling cost.
The point of no return is the moment Epicor is set read-only and D365 is opened to users. Before that point, rollback means "reopen Epicor and reschedule the cutover." After that point, once external parties (customers, vendors, banks, EDI partners) hold data referencing D365, rollback in the restore sense creates a worse reconciliation…
The cutover is not complete when the data loads. It is complete when users can transact. Day-one readiness requires:
Hypercare is not "support with extra people." It is a structured de-escalation from a command-centre posture to steady-state operations, driven by evidence rather than elapsed time.
The Epicor system does not disappear at go-live. It transitions through three post-cutover states:
The cutover is the event that validates or exposes the entire programme. It succeeds when four-corner reconciliation is green, the go/no-go decision is made on evidence, and users can transact on day one.