Phase 04 of 08
Data migration
Typically 5-15% of total project cost. Extracting, cleansing, transforming, and loading data from legacy systems. Range is wide because the dirtier the source data, the more this phase costs.
What's included
- ETL development for each legacy source
- Data-cleansing rules and tooling
- Trial migrations (typically 3-5 rounds before go-live)
- Reconciliation reporting
- Cutover plan and rehearsal
- Archival of legacy systems
Common overruns
- Discovery that legacy data quality is far worse than assumed
- Multiple legacy ERPs that disagree on the same record
- Trial migration cycles that surface new validation rules each time
Source
Third-party aggregator synthesis 2026 (5-15% of total).
Verified 2026-06-02
Other phases