Choose a system of record and import only fields required by approved journeys. Keep consent source and purpose traceable. Define duplicate, correction, deletion and retention handling with the business owner.
Data preparation
Standardise phone-number format, field names and allowed values before import. Separate operational attributes from free-form notes and avoid importing credentials, payment details or unnecessary sensitive data. Test mapping on a small reversible sample.
Ongoing governance
Assign owners for merge decisions, access reviews and deletion requests. Record how updates flow back to the system of record, and monitor integrations for stale or conflicting values.