What happens to duplicates when I import?

Rows that match an existing donor are flagged as possible duplicates in Import results, and you choose Add as new, Merge or Delete for each one.

Donors doesn't create a second record for a row that matches someone already in Donors. It flags the row as a possible duplicate in Import results, and you click Resolve to decide.

Details

A row matches an existing donor when it has the same email, or the same name plus the same phone or city. The row's Detail says which.

For each flagged row, choose:

Merge keeps the existing record and fills in details from the file.
Add as new creates a separate contact from the row.
Delete discards the row; nothing is imported from it.

Gifts on the same row are attached to the matching existing donor when they're imported. Resolving happens after the clean rows are written, and you can reopen the import from Import history in Organization Settings → Data & audit to finish later.