Moving customer data is the riskiest part of changing systems. Most problems come from messy data and rushed testing, both of which you can avoid.
Clean before you move
Moving duplicates and dead records only moves the mess.
- Merge duplicate customers
- Remove contacts you no longer need
- Fix obvious spelling and format problems
- Decide what history is worth keeping
Map the fields
List every field in the old system and where it goes in the new one. Decide what to do with fields that have no match, so nothing disappears quietly.
Test on a copy
Import a sample first, check twenty records by hand, then import everything. Keep the old system available and read only for at least a month.