The ERP data migration checklist: zero-loss in practice

Ask anyone whose ERP project overran and the story usually turns to data: the customer master that existed in four versions, the item codes nobody could explain, the opening balances that would not reconcile. Migration is not a technical afterthought; it is a project inside the project, and it starts on day one.

Phase 1: scope and ownership

1. List every data object: customers, suppliers, items, BOMs, price lists, open orders, open invoices, balances, history.
2. For each, decide: migrate live, load as opening balance, or archive for reference.
3. Name one business owner per object. Not IT: the person who can say 'this customer list is correct'.
4. Agree the cutoff strategy: what happens to transactions created between extract and go-live.

Phase 2: clean at the source

1. Deduplicate customers and suppliers; agree naming conventions and coding schemes.
2. Standardise TRNs, phone formats and addresses; the 2027 e-invoicing mandate will punish dirty tax records, as our readiness page explains.
3. Kill zombie items: anything with no stock and no movement in 24 months gets archived.
4. Resolve negative stock and unmatched receipts before extraction, not after.

Phase 3: map and trial

1. Build a field-by-field mapping document; every target field has a source or an explicit default.
2. Trial load one: expect failures, log every rejection, fix at source, re-extract.
3. Trial load two: full volume, timed, with the reconciliation report drafted.
4. Freeze the mapping. Late mapping changes are how 'one more fix' becomes three more weeks.

Phase 4: reconcile and sign

1. Counts match: customers, suppliers, items, open documents, to the row.
2. Values match: AR, AP, stock valuation and trial balance against the source, to the fils.
3. Spot-check depth: ten real records traced end to end by the business owner.
4. Finance signs the reconciliation. That signature is the UAT gate; nothing goes live without it.

This is unglamorous work, which is exactly why it separates implementations that land from those that limp. It is also why we put validated migration inside the fixed price rather than selling it as a change request later.