Acquisition ignored default rate by channel.
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Fintech · Lending

Acquisition ignored default rate by channel.

This marketing & margin audit surfaced $88k in recurring annual margin in a Fintech business — evidenced, senior-reviewed, and delivered in 7 days.

$3–8M annual revenue Lending Focus: Default by channel
+27%
risk-adjusted CAC
+27%
risk-adjusted margin
7 days
to findings
Risk-adjusted acquisition cost per loan
Before audit
$540
After fix
$400

The business

A consumer lender acquired borrowers across several marketing channels, judging each on its approved-loan customer-acquisition cost. Origination volume was healthy and the channels were treated as broadly comparable on that CAC, so the way default rates — the single biggest driver of lending profitability — varied by acquisition source was never built into the channel comparison.

What triggered the audit

Portfolio margin varied more than a comparable approved-loan CAC could explain, pointing at credit performance rather than acquisition cost. The audit split loan-book performance by acquisition channel, testing whether borrowers from different sources defaulted at materially different rates once the loans were on the book.

What the audit found

Judging channels on approved-loan CAC alone had hidden a decisive difference in credit quality. When default rates were split by acquisition source, some channels that looked efficient on CAC were bringing in borrowers who defaulted at materially higher rates, so their true risk-adjusted cost was far worse — while other, apparently pricier channels delivered better-performing loans that were genuinely more profitable. Because default is a lagging cost that lands months after origination, and channels were compared only on upfront CAC, the poor-performing sources kept attracting budget on economics that ignored their losses. Reweighting acquisition toward the channels with stronger risk-adjusted performance improved risk-adjusted CAC by 27%.

How we produced this finding

Behind the default by channel finding is real cohort analysis: MarginFix measured what fintech customers genuinely did over time instead of projecting from early signals, then had a named senior auditor verify the evidenced read against the client’s own data before it reached leadership.

Data sources: Cohort-level acquisition, retention and revenue data tracked over time, joined to fully-loaded acquisition cost, so default by channel is judged on genuine lifetime behavior and where it actually breaks down rather than a day-one snapshot.

Key frameworks: Cohort retention-curve and LTV:CAC modeling, incrementality testing and full-cost payback analysis, framed by the Bain CMO Effectiveness Framework for contribution and full-funnel efficiency.

Human validation gate: Every cohort read is re-run against your own data and signed off by a named senior auditor before it ships — no model output is ever presented unreviewed.

Verified against
Transaction ledger CAC / funnel analytics Unit-economics model Finance P&L

The risk-adjusted CAC was measured like-for-like over a matched period, reconciled to recognized revenue in the ledger, and signed off by a named senior auditor before publication. Client identity redacted to protect their commercial position.

WORKING PAPER ████████ Lending
Representative Redacted
ChannelRisk-adj. CAC
Referral
$360
Organic
$410
High-default channel
$540
risk-adjusted CAC +27%
Durable — the improvement holds every year the fix stays in place, not a one-off.
Working paper: risk-adjusted acquisition cost per loan traced line by line and reconciled to recognized revenue in the ledger over a matched period. Line items representative and redacted; the recovered figure is the reconciled audit finding.

What we changed

Split loan-book default performance by acquisition channel, exposing the true risk-adjusted cost that a comparison on upfront CAC completely concealed.

Reweighted acquisition toward the channels delivering better-performing loans, and cut those consistently bringing in high-default borrowers.

Built risk-adjusted CAC — acquisition cost plus expected losses — into channel reporting and budgeting, so decisions reflect credit quality.

Tightened targeting and credit criteria on the channels that were retained but prone to weaker performance, improving the quality of the loans they do bring onto the book.

The result

Risk-adjusted CAC improved 27% by acquiring borrowers who actually repay, not just those who are cheap to originate. For any lender, upfront CAC is the trap: default lands months later, so a channel that looks efficient can be quietly loss-making. If you compare channels before their loans season, you may be scaling your worst credit. It takes splitting default by source to see it — a fixed-fee audit does that in days, before more budget follows the losses.

From kickoff to signed-off findings: 7 days — inside our fixed 5–7 day window.

This +27% risk-adjusted CAC gain is ≈$88k/yr at the client’s revenue scale.

Reviewed & signed off by:
MarginFix Audit Team
Senior Auditor · MarginFix · 10+ years of auditing experience
Anonymized to protect the client · senior-reviewed findings · Last reviewed
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