Every CiviCRM database ends up with duplicates eventually — someone donates once as “Jon Smith” and again as “Jonathan Smith”, or a couple gets entered as two separate households instead of one. It's normal, and it's fixable.

CiviCRM has a built-in dedupe tool that finds likely duplicates based on rules you can tune — matching on email, name, address, however strict you want to be. The bit people worry about is losing donation history when two records merge. It doesn't. Contributions, memberships, activities and notes all move across to the surviving record.

Our advice: don't try to fix years of duplicates in one sitting. Run the dedupe tool regularly, in small batches, and check a handful of matches before you merge them in bulk. It's much less daunting that way, and far less likely to merge two people who just happen to share a name.