The Complete Legal Data Migration Checklist: 47 Steps to a Successful System Migration

A legal data migration is one of the highest-stakes technology projects a law firm will undertake. Done well, it's the foundation for years of improved efficiency and better client service. Done poorly, it can mean lost data, billing disruptions, compliance failures, and months of painful cleanup work.

At Denim, we've completed over 700 legal data migrations across practice management systems, document management systems, and knowledge bases. We've migrated firms from every major legacy platform to Clio Manage, ActionStep, Smokeball, iManage, NetDocuments, and more. This checklist distils that experience into 47 steps across six phases.

Use it to plan your own migration, to evaluate a migration partner's methodology, or to identify gaps in a migration project that's already underway.

Phase 1: Discovery and Scoping (Weeks 1–2)

The most important work in any migration happens before a single record is moved. Skipping or rushing this phase is the most common cause of migration failures.

1. Conduct a full audit of all source systems — PMS, DMS, email archives, shared drives, and any other systems containing client or matter data
2. Document the total data volume: number of matters, contacts, documents, time entries, billing records, and trust ledger entries
3. Identify all data relationships and dependencies (e.g., matters linked to contacts, documents linked to matters)
4. Map source data fields to destination data fields — document every field that exists in the source and where it will land in the destination
5. Identify fields that don't have a direct mapping and decide: transform, discard, or store as a custom field
6. Document all custom fields, custom matter types, and custom billing codes in the source system
7. Identify data quality issues: duplicates, incomplete records, inconsistent coding, orphaned records
8. Agree on the data quality remediation scope — what will be cleaned before migration vs. after
9. Define the migration scope: what data will be migrated, what will be archived, what will be discarded
10. Establish the go-live date and work backwards to set phase milestones

Phase 2: Data Preparation and Cleanup (Weeks 2–4)

Clean data in a new system delivers exponentially more value than dirty data. This phase is often underestimated — budget at least as much time for data cleanup as for the technical migration itself.

11. Deduplicate contact records — merge or delete duplicate clients, contacts, and organisations
12. Standardise contact data formats: phone numbers, addresses, email addresses
13. Verify and correct matter coding: practice area codes, matter types, billing codes
14. Identify and handle open matters with billing anomalies: negative WIP, unallocated trust funds, unbilled disbursements
15. Archive or close matters that have been inactive for more than 7 years (check your jurisdiction's retention requirements)
16. Audit trust account records — reconcile trust ledger against trust bank statements before migration
17. Identify documents that are outside the DMS (email attachments, local drives, SharePoint) and decide whether to include them in scope
18. Standardise document naming conventions if required by the destination system
19. Remove or archive documents that are clearly not client-related (software installers, personal files, etc.)
20. Create a data quality report documenting all issues found and actions taken

Phase 3: Technical Migration Setup (Weeks 3–5)

21. Set up the destination system with all required configuration: matter types, billing codes, user accounts, permission structures
22. Configure integrations that will be needed on day one: email, accounting software, document management
23. Build the migration scripts or configure the migration tool — document every transformation rule
24. Establish a test migration environment that mirrors production
25. Run the first test migration with a representative sample of data (10–20% of total volume)
26. Validate the test migration against the field mapping document — check every mapped field
27. Document all issues found in the test migration and update migration scripts accordingly
28. Run a second test migration with the full dataset
29. Conduct user acceptance testing (UAT) with key stakeholders — have them verify their own matters and documents
30. Document and resolve all UAT issues before proceeding to production migration

Phase 4: Go-Live Preparation (Week Before Go-Live)

31. Communicate the go-live plan to all staff — date, what will change, what training is available
32. Schedule go-live for a Friday afternoon or long weekend to minimise disruption
33. Prepare a rollback plan — document exactly what steps to take if the migration fails and you need to revert to the source system
34. Confirm all integrations are configured and tested in the destination system
35. Prepare the trust account reconciliation report as of the migration date
36. Brief all staff on the new system: key workflows, where to find things, who to contact for support
37. Set up a dedicated support channel for go-live week — a Slack channel, Teams channel, or email alias where staff can report issues

Phase 5: Production Migration (Go-Live)

38. Take a final export/backup of the source system immediately before migration
39. Run the production migration — monitor progress and log any errors in real time
40. Validate critical data immediately after migration: active matters, trust balances, recent time entries
41. Verify all integrations are working in the production environment
42. Conduct a final trust account reconciliation in the destination system
43. Confirm the source system is in read-only mode (not decommissioned yet — you may need it for reference)

Phase 6: Post-Go-Live Validation (Weeks 1–4 After Go-Live)

44. Monitor the support channel daily for the first two weeks — triage and resolve issues quickly
45. Run a data completeness check at the end of week one: are all expected matters, contacts, and documents present?
46. Conduct a billing run in the new system and reconcile against expected figures
47. Decommission the source system only after 30 days of stable operation in the destination system — and only after confirming all data has been successfully migrated and validated