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Insights and Expertise

once 44 percent of that month's fees, inflating any month-
Put two of these analysts on over-month comparison that included it. And on a dual-
priced account the headline rate read 3.6461 percent while
opposite sides of a deal and the merchant's own cost of acceptance was 0.0328 percent,
because the surcharge collected from cardholders settles
the comparison becomes an inside card volume and pays most of the bill. Both num-

artifact of method rather than bers are defensible. They differ by a factor of 111.
a fact about the merchant. Publish the rounding rule as part of the equation. Money
work should not depend on floating-point behavior or
whichever mode is active in someone's spreadsheet. Our
model rounds the effective rate half up to six decimal plac-
Declare the corollary too — fees arising from credits and es and average ticket to two; 0.022918 displays as 2.2918
disputes stay in the numerator even though credit volume percent. That feels fussy until two systems disagree at a
never enters the denominator. That is a stated convention, boundary, at which point a disclosed rule turns an argu-
not an oversight, and it biases the rate upward for a high- ment into a testable question.
return merchant.
Say plainly what the number cannot prove
Then reconcile the numerator. "Total fees" hides several A validator can prove that required fields exist, that fee
different totals. Classify every processing-related charge groups reconcile, that dates are ordered and that com-
exactly once: interchange, assessments, processor markup, puted fields match declared inputs. It cannot prove a hu-
authorization, monthly, PCI, equipment, chargebacks and man transcribed the source correctly, decide whether a
an explicit other for genuinely ambiguous costs. fee is contractually permitted, or say whether a merchant
should switch providers.
Tiered and flat-rate statements need one more category,
because they print a single blended discount that fuses It cannot even tell you that the line labeled interchange
interchange, assessments and markup and cannot be is interchange—a padded pass-through reconciles to the
taken apart from the document; a bucket like that should cent and validates clean. Catching that takes the brand's
say so rather than be filed under whichever component it published tables and transaction detail, which no state-
most resembles. Gross processing fees are the exact sum ment-level record carries. The contract makes the arithme-
of those groups. Net processing fees are gross fees minus tic checkable, not the pricing honest.
processing-fee credits. Only then divide.
That distinction belongs in the audit itself. "The arithmetic
This matters more than it sounds, and it is worth checking reconciles" is defensible. "This merchant is definitely over-
on your own desk today. On several common statement paying" usually is not, unless the reviewer can name the
formats the processor's discount is printed below the item- comparison basis and the assumptions behind it.
ized fee total rather than inside it: the statement shows a
total fees due figure, a separate discount due figure, and American Express deserves its own line, because it moves
an amount deducted that equals the two added together. the denominator without touching the numerator: under
An analyst who sums the fee sections and stops at the OptBlue the discount sits on the acquirer statement, while
printed total omits the markup entirely. a direct agreement bills off it, leaving the volume inside
the comparison and the cost outside.
I ran that check across 68 real monthly statements from
two unrelated processors. On one, itemized-only report- Source statements also stay private. A reusable audit re-
ing gave 3.0701 percent against an all-in 3.8701 percent cord needs statement-level totals only —never card num-
— 80 basis points, roughly a fifth of what the merchant bers, security codes, PIN data, bank or routing numbers,
actually paid, missing. On another, 2.9050 against 3.5050 tax identifiers or credentials. Automated screening reduc-
percent. On a third format, 20 basis points. Same docu- es accidental disclosure; it does not replace a human read-
ment, same analyst, two defensible readings, and nothing ing the record before it leaves the merchant's control.
on the page announces which one you just performed.
Six lines to write down before you quote a rate
The same corpus made three other habits measurable.
Eleven statements produced an effective rate above 100 None of this requires new software. It requires writing
percent—dormant months where fixed fees dwarfed a six things at the top of the analysis, before the arithmetic
few dollars of volume, the worst reading 8,037 percent— starts, and letting the merchant see them.
arithmetically true, analytically worthless, and belonging • State the period and the volume definition—gross
flagged rather than averaged into anything. settled purchase volume and its matching settled
count, named as such.
Seven carried an annual charge inside a single month,
• State the numerator: every processing charge for that
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