Salesforce Lead Import Best Practices Before You Upload a CSV

A reliable Salesforce Lead import starts before the upload screen. The CSV needs valid structure, stable matching fields, and a deliberate plan for records that already exist elsewhere in the org.

Pre-import checklist

1. Keep a source copy. Preserve the original Lead list before cleanup.
2. Validate the CSV. Check headers, row widths, encoding, required values, and spreadsheet damage.
3. Choose a meaningful exact key. Email is common; a stable external ID is stronger when available in both datasets.
4. Export current Contacts. Include the same exact key.
5. Run a Lead-vs-Contact preflight. Review collisions separately from new Leads.
6. Check mapping and defaults. Confirm Lead Source and any required custom fields in your Salesforce import process.
7. Use a preview or small test batch when practical. Confirm that field mapping and duplicate rules behave as expected before the full list.
8. Keep an audit trail for important imports. Record the source file, date, key used, and how collisions were handled.

Why exact preflight comes before deduplication

Flat-file deduplication can remove repeated rows inside one CSV, but it cannot tell you that an incoming Lead already exists as a Contact in Salesforce. That requires comparing the Lead list with an exported Contact population.

Use Validate CSV for structure and the Salesforce Lead preflight for cross-object collisions.

Preflight a Lead CSV

See the transformation

A useful diff separates every kind of change.

See changed, added, and removed rows separately so you know exactly what needs attention.

Result

Changed1001, starter1001, pro

Removed1004, pro

Added1006, pro

Changed rows1

Added rows1

Removed rows1