Context
Ask most businesses where their leads come from and the honest answer is a shrug — a third of the CRM says "unknown." SourceTrace is a privacy-safe recreation of a real build — the fix: attribution as a discipline, not a guess.
The problem
When 31% of leads are untagged, every budget decision is fiction. Spend keeps flowing to the loudest channel (paid search) while the highest-ROI ones (Google Business Profile, organic) go underfunded because nobody can prove their contribution.
The approach
I built the reconciliation layer and its dashboard: a standardized UTM schema across campaigns, GA4 and call tracking reconciled against the CRM source field, GBP quote-requests tagged separately from map views, and a weekly auto-audit that flags any lead missing a source. On top: a source breakdown, blended cost-per-lead, and an ROI-by-channel table.
What the build shows
Untagged leads down from 31% to 4% — and the story the clean data tells: Google Business Profile returning 9.8x on $1,200 of spend while paid search returns 2.4x on $18,900. That one table reprices an entire marketing budget.
Recreated for confidentiality — a faithful, fully-working mimic of a real production build; client names, branding and data have been fictionalized.