Sequence the load waves against a company-database boundary, rehearse the cutover until it is boring, and build the reconciliation evidence that finance and audit will actually accept.
Cutover is where every earlier decision is tested at once, under time pressure, in front of people who will remember the outcome.
The canonical wave order applies, and the playbook's suggested plan maps onto it directly.
The source validation set is the right starting point because it is what finance and operations recognise:
A rehearsal is not the first execution of the sequence. It is a timed, complete, realistic run that produces the evidence needed to plan the real one.
The cheapest cutover work happens in the source system in the weeks before the freeze. Every item cleared is an item that needs no migration design, no test case and no reconciliation line.
History does not migrate. Only open and required state carries — the concept mapping says so for production, the posting rules say so for inventory revaluation, and the same logic applies across the estate.
The decision is made on evidence, against criteria agreed in advance and written down before anybody is tired.
The first close is the real test. Every posting design decision surfaces. Staff the close with the people who made those decisions, not only with support.
The company database is a natural cutover and reconciliation unit. Preserve the alignment. Eight waves, each gated. Configuration, masters, open documents, inventory, open production and assets, subledger open items, opening balances, delta.