The category nobody owns
On most multi-unit finance teams, payment processing is somebody's fourth priority. It is reviewed at renewal, benchmarked against a single competing quote, and then left alone for three years while card volume grows.
In that window the effective rate drifts. Assessments change, card mixes shift toward premium rewards products, and the markup that looked competitive at signing quietly becomes 60 to 80 basis points of pure spread on every dollar of card volume.
Where the spread hides
Interchange is set by the networks and is not negotiable. Everything above it is: processor markup, per-transaction fees, monthly minimums, PCI programs, gateway fees, batch fees, and non-qualified downgrade buckets that trigger when data is submitted incorrectly at the POS.
Downgrades are the most expensive and least visible item. A card-present environment that submits incomplete data can push a meaningful share of transactions into higher interchange tiers — a problem that looks like interchange on the statement but is really a configuration issue.
What it is worth
Take a 70-unit fast-casual chain at $105M in system sales with 80% card penetration. That is roughly $84M of card volume. Seventy basis points of recoverable spread is about $588K a year — recurring, with no guest-facing change and no menu price move.
That is one category. It is also the fastest to prove, because the evidence is already in twelve months of merchant statements.
How to audit it yourself
Pull three consecutive months of full merchant statements for every entity, not the summary page. Compute effective rate as total fees divided by total volume, per location. Then separate interchange from everything else.
Spread across locations is the tell. When two similar stores post materially different effective rates on similar tickets, the difference is configuration or contract — not card mix.
Takeaways
Interchange is fixed; markup, downgrades, and ancillary fees are not.
Effective rate per location, not blended, is the number that exposes the leak.
Seventy bps on $84M of card volume is roughly $588K a year, recurring.