Why Durbin matters
The Durbin Amendment did two things in 2011: (1) it capped debit-card interchange for issuers with $10 billion or more in assets, and (2) it required all debit transactions to be routable across at least two unaffiliated networks. The result was a structural divide in US debit economics: large banks earn capped interchange; small banks ("Durbin-exempt" issuers) earn uncapped, market-rate interchange.
For a fintech, this single regulatory line is the largest driver of which banks make good BIN-sponsor partners. A Durbin-exempt sponsor bank can pass through 2–4x the interchange of a covered bank on the same debit transaction.
When Durbin matters most
It matters most when: (a) selecting a BIN sponsor, where exempt vs covered status defines the ceiling on your interchange economics; (b) evaluating sponsor-bank growth risk, since crossing the $10B asset threshold immediately re-prices their entire debit book; and (c) planning network-routing strategy, since Reg II's dual-network requirement gives you real economic optionality.
Common pitfalls
- Modeling on a sponsor that will graduate. A bank approaching $10B in assets may be exempt today and covered next quarter. Read the runway.
- Ignoring routing economics. Even on Durbin-exempt issuers, the choice of routing network materially affects your effective interchange.
- Pending reform. The Fed has proposed lowering the existing cap further. Stress-test your model against the proposed numbers.
Durbin is why small banks are the natural home for fintech debit programs \u2014 know the threshold and design around it.