Anyone who has ever moved data from one system to another has almost certainly run into duplicate records on the other side, especially when moving from multiple tools that were similar into a single workspace.
This could be contact information that appears twice, or projects and tasks created once during a test run and again during the live migration.
Duplicates during migration are a predictable part of moving data, and they are manageable when you go in prepared.
The most common cause is pulling from multiple sources without checking first. Using more than one place before the migration, which most businesses do so information accumulates across tools and spreadsheets over time, means records that refer to the same thing arrive from different sources. A contact that exists in your project management tool, your CRM, and a shared spreadsheet will arrive as three separate records.
Another cause is inconsistent formatting. Records that should match each other do not, one might say “Abc” and another says “ABC Limited.” The system will treat them as different though they are technically different, but they refer to the same business.
The best approach is to run a deduplication check on your source data before and after migrating. Standardise formats for company names, contact names, and project titles. For me, it is much easier to do this in the new system after everything has moved, since I can tag the sources of all data, check for duplicates, and consolidate where necessary.
When duplicates have already landed in the new system, most platforms have a merge function. Use it carefully and make sure any activity or history attached to a duplicate record is preserved before the merge.