Assess before you move
Not all historical data deserves to migrate. Separate records with active business value from data kept only for comfort, because migrating everything makes the new system harder to trust on day one. A common mistake is treating migration as an exercise in completeness rather than judgement. Ask of each data set: will anyone make a decision with this in the next year? If the answer is no, archive it where it can still be read, but do not put it in the live system. Users judge a new CRM by what they see in the first week.
Agree the field mapping in writing
Ambiguous values are the main source of post-migration complaints. Decide how unmapped or conflicting values are handled before the first import, and have that document signed off by the people who will actually use the data. Include the boring details: date formats, country and currency codes, owner names where staff have left, and free-text fields that mean three different things. A mapping document also forces useful conversations about which fields are genuinely required versus which were only ever populated out of habit.
Set deduplication rules first
Decide what makes two records the same — email, phone, company domain, or a combination — and write the rule down before the import. Deduplicating afterwards is far more painful, especially once related records such as deals, tickets and activities are attached to the wrong copy. Also decide precedence: when two records conflict, which one wins? Without a rule, teams resolve conflicts inconsistently and the database quietly loses reliability. Run a duplicate report on a sample of data before migration to see how large the problem actually is.
Test in batches, then reconcile
Import in stages, starting with a representative sample, and review validation reports after each batch rather than only at the end. Keep the legacy system readable until sign-off is complete: the ability to check the old source is what turns migration anxiety into confidence, and it disappears the moment you switch it off. Reconciliation should be specific — record counts, a sample of high-value records checked field by field, and totals that match the old system. Vague spot checks miss exactly the errors that matter.
Decide what history to keep and where
Closed deals, old tickets and lapsed contacts may matter for context but not for daily work. Decide what moves into the live system, what goes to an archive that remains searchable, and what is genuinely disposable. Carrying everything forward slows the system down and clutters every list view, which is a real adoption cost. A useful test: if a user would never open the record in the normal course of their week, it belongs in the archive. Compliance requirements, of course, override this — check them first.
Reassign ownership and permissions deliberately
Migration is a good moment to correct years of accumulated permissions. Map old owners to new roles, retire accounts belonging to departed staff, and resist the temptation to give everyone administrator access simply to avoid questions during cutover. Broad permissions granted for convenience tend to survive long after the migration is finished, and they quietly undermine data quality and reporting. Design roles around what each function needs to see and do, then test the setup with a real user before go-live, not after.
Plan the cutover day realistically
Choose a low-activity window, freeze edits to the old system, tell every affected team what will happen and when, and have a rollback plan that has actually been written down. Most failed migrations fail on coordination rather than tooling. Assign someone to be visibly available for questions, decide in advance who has authority to call off the cutover, and confirm the freeze is technically enforced rather than merely requested. A calm, boring cutover is the result of planning, not luck.
Check the first 30 days after go-live
Watch for duplicate creation, missing attachments, automations that stopped firing and reports that disagree with the old numbers. A short, structured post-migration review catches issues while people still remember how the old system behaved — after a few months, nobody can tell you whether a figure is wrong or was always wrong. Ask users for specific friction rather than general feedback, and fix the top three items quickly. Visible early responsiveness does more for adoption than any amount of training.