You capture the marketing source perfectly on the Salesforce lead. Then the lead converts, an opportunity is created, and the source is gone. This is the single most common and most damaging break in B2B attribution, because it fails late — after everything upstream worked. It’s the Salesforce version of the inheritance break described in the attribution gap.
What actually happens at conversion
When a Salesforce lead converts, standard fields map to the account, contact, and opportunity automatically, but custom fields do not. Any UTM or source field you added is custom, so unless you have explicitly mapped it, Salesforce simply doesn’t carry it across. The data isn’t deleted from the old lead, but it never reaches the opportunity where revenue reporting happens.
How to set up lead conversion field mapping
In Setup, open the Lead object’s field mapping (Object Manager → Lead → Fields & Relationships → Map Lead Fields). For each source field on the lead, map it to the corresponding custom field on the contact and the opportunity. This means the matching custom fields have to exist on all three objects first — create them on contact and opportunity, then map lead → each.
Map to the opportunity, not just the contact
Mapping to the contact alone isn’t enough. Revenue lives on the opportunity, so the source has to reach the opportunity to appear in closed-won reporting. Map first-touch and last-touch fields both — each answers a different question — so a won opportunity carries its full origin story.
Verify it worked
Convert a test lead with known source values and confirm the fields populate on the resulting opportunity, not just the contact. Then build the report that groups closed revenue by source — the closed-loop report that turns attribution into a budget decision.
Frequently asked questions
See where your revenue is leaking
The Rapid Alignment Audit maps exactly where your marketing-to-sales handoff breaks — and hands you a prioritized fix you keep either way.
Book the Audit →