Here are some ways to remove duplicate records before importing data into Salesforce:
- It is easier to remove duplicates from a spreadsheet than in Salesforce.
- The Salesforce import wizards will attempt to merge duplicate accounts, contacts and leads but you will stand a better chance of a clean import if you clean them yourself before importing your data.
- So remove your duplicates in Excel.
- Then use the Data Loader, or Excel Connector, (neither of which will attempt to merge any duplicates), or the import wizard to import the clean data.