Common Salesforce Lead Import Collisions with Existing Contacts
Understand why Salesforce Lead imports collide with existing Contacts and how an exact-key preflight helps you review those records before import.
Salesforce can reject or complicate a Lead import when the incoming person already exists as a Contact. The underlying issue is cross-object identity: a Lead and a Contact are different Salesforce records even when they share an email address or another business key.
Salesforce error: DUPLICATE_VALUE
Salesforce can return DUPLICATE_VALUE when an imported value conflicts with a field configured as unique. Check the failed-row CSV from Salesforce, identify the unique field named in the error, and compare the incoming values with existing records before retrying the import. Salesforce documents this error in its Data Import troubleshooting article.
For Lead imports, a preflight against existing Contacts is useful before the upload because it exposes exact-key overlaps that should be reviewed instead of creating another CRM record blindly.
Collision patterns to review
The same email already exists on a Contact
This is the clearest exact-key collision. Review whether the incoming row should update an existing process, be skipped, or be handled through your organization’s conversion and duplicate-management rules.
The chosen key is blank or duplicated
An empty key cannot establish identity. A duplicated exact key inside either export is also ambiguous. Fix those source rows or choose a stronger identifier before relying on the preflight result.
The Contact export is stale
A new Contact created after the export will not appear in the comparison. For recurring imports, export Contacts close to the import time.
Similar names are not exact identifiers
Do not treat a similar company or person name as an exact match unless that is an intentional business key. This tool deliberately does not perform fuzzy matching.
A useful response to a collision
Review the Contact in Salesforce, decide what the incoming row represents, document the decision when the import is sensitive, then keep only records that should genuinely be created as Leads in the final import CSV.
The Lead vs Contact preflight tool keeps this review separate from the new-only export.
Review Lead collisionsSee the transformation
A useful diff separates every kind of change.
See changed, added, and removed rows separately so you know exactly what needs attention.
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Review Lead collisionsRelated tools
Open the tool this guide is about, or explore a related one.
- Compare CSV files online freeCompare two CSV files and review added, removed, and changed rows directly in your browser.
- Validate CSV files online freeScan a CSV once for structural, encoding, header, delimiter, and whitespace problems without changing the file.
- Salesforce Contact-to-Account Import JoinerMatch Salesforce Contacts to Accounts, append AccountId only for unique matches, and review unmatched or ambiguous rows before import.