Inventory the information you need
List the systems and files involved, the person responsible for each source and the records worth carrying forward. Separate active customer information from obsolete exports and material with no continuing purpose. Identify attachment types, historic notes, currencies, dates and custom fields early; these often require more preparation than a contact name.
Agree a field map and duplicate rules
For each source field, record its destination, format and whether a transformation is needed. Decide how to match organisations and contacts without treating a shared email address or similar business name as proof of identity. Preserve an appropriate source identifier so the migration team can reconcile records without exposing it unnecessarily to every user.
Test representative records safely
Use a controlled sample containing common records and known exceptions. Check linked contacts, ownership, dates, totals and permissions. Keep sensitive personal information out of casual email attachments and use an agreed secure transfer route. Confirm who is allowed to view the sample and when temporary migration files will be removed.
Reconcile before switching the team over
Agree record counts, spot checks and acceptance criteria before the final import. Plan how changes made during migration will be captured and who approves the transition. Confirm recovery and export arrangements with the service team, then retain only the migration evidence and source material your organisation actually needs.