Clean the source before importing
Identify the latest approved employee list and remove duplicate records through a documented review. Standardise dates and component names. Keep original files intact so a changed value can be traced, and avoid assuming that similarly named columns mean the same thing across departments.
Map fields and opening values
Document where each source field belongs in the new system. Agree the effective date for salary structures and leave balances. Test representative records, including a joiner and an employee with variable inputs, before expanding to the full population.
Reconcile a parallel run
Process the same approved inputs through both methods and compare employee-level results. Investigate differences rather than copying the old total into the new system. Some differences may reveal an old error; others may indicate an incorrect mapping or configuration.
Worked example
One workbook stores dates as day/month/year while another uses month/day/year. A test import containing dates above the twelfth day helps expose an interpretation problem before the full migration.
Practical checklist
- Keep an approved source snapshot.
- Document field mappings and effective dates.
- Resolve parallel-run differences before switching.