Everything in the earlier modules describes costs the merchant ultimately pays. Interchange goes to the issuer, scheme and network fees go to the network, and the acquirer adds a markup for moving the transaction and carrying the risk. The merchant sees none of those parties directly. It sees one number on a statement, and that number is where most of the confusion, and most of the overcharging, lives.
This module is about that number: what the merchant discount rate actually contains, how pricing models repackage it, and how to read a statement closely enough to know whether you are being charged the true cost or something padded on top.
What the merchant discount rate is
The merchant discount rate (MDR) is the all-in percentage a merchant pays its acquirer to accept a card payment. It is not a single fee paid to a single party. It is the sum of three layers stacked together: interchange (set by the network, paid to the issuer), scheme and network fees (paid to the network), and the acquirer markup (the processor's margin).
Across US merchants, the all-in cost typically lands between roughly 1.5 percent and 3.5 percent of each transaction, plus a small fixed per-transaction fee of around 10 to 30 cents. Where a given merchant sits depends on card mix, channel, ticket size, merchant category, and how hard the merchant has negotiated. Small merchants tend toward the high end. Merchants doing more than $10 million a year in card volume often negotiate effective rates closer to 1.5 to 2.0 percent.
The two bottom layers are largely fixed. Interchange is published by the networks, and assessment fees run around 0.13 to 0.15 percent. Visa's assessment is about 0.14 percent on consumer credit and 0.13 percent on consumer debit; Mastercard's is 0.13 percent below $1,000 with a small add-on above it. Neither is negotiable. The only layer the merchant can actually move is the acquirer markup, which is exactly why pricing models matter.
Pricing models: blended versus interchange-plus-plus
Blended pricing
Blended pricing gives the merchant one flat rate regardless of what card is presented. A typical quote looks like 2.9 percent plus 30 cents. It is simple to budget and simple to sell, which is why it dominates among small merchants and is the default for flat-rate aggregators.
The problem is that the flat rate has to cover the most expensive cards the merchant might accept, so on cheaper transactions, debit, regulated cards, low-cost credit, the processor keeps the difference. The merchant cannot see that difference, because blended pricing fuses all three layers into one figure. You cannot tell what is interchange, what is network fee, and what is markup.
Interchange-plus-plus (IC++)
Interchange-plus-plus prices each layer separately. The statement passes through actual interchange at cost, passes through actual scheme and network fees at cost, and shows the acquirer markup as its own explicit line, usually quoted as basis points plus a per-transaction fee. The two "plus" signs refer to the two pass-through layers (interchange and scheme fees) sitting on top of the base.
The value of IC++ is legibility. When interchange and network fees are pass-through, the merchant can see exactly what the processor is actually charging for, and that number is the only thing left to negotiate. A markup quoted as "interchange plus 0.20 percent plus 8 cents" is a contract you can hold the processor to. A blended 2.9 percent is not, because you have no idea what is underneath it.
There is a tradeoff. With IC++, the effective rate moves month to month as the card mix shifts, because interchange itself varies. A month heavy on premium rewards cards costs more than a month heavy on debit, and the statement will show it. Merchants used to a flat number have to get comfortable with a rate that breathes. For most merchants above a modest volume, the net cost under IC++ is lower, because they stop subsidizing the processor's margin on cheap transactions.
Reading the statement
Find the effective rate first
Before parsing any line item, calculate the effective rate. Take total fees for the month, divide by total card volume, and you have the real all-in cost. A processor's quoted rate and the merchant's effective rate are frequently different numbers, and the gap is the whole point of doing the arithmetic.
For reference, the average effective swipe fee across Visa and Mastercard in 2025 was around 2.36 percent. If a merchant accepting mostly debit and card-present transactions is running an effective rate well above that, something on the statement is doing work that needs explaining.
Watch for downgrades
A downgrade is when a transaction fails to qualify for its lowest-cost interchange category and gets routed to a more expensive one. Common causes are missing address verification data, settling a batch too late, keyed-in transactions without full data, or magnetic-stripe data where chip data was expected. Visa's EIRF and the Standard fallback tiers are typical downgrade buckets.
Under IC++ you can see downgrades, because each transaction's interchange category is itemized. Under blended pricing you usually cannot, which is convenient for the processor, since downgraded transactions tend to flow to its non-qualified tier where the margin is widest. Many downgrades are operational and fixable: enable AVS, settle daily, capture full card data at the terminal.
A worked example
Take a merchant running $200,000 in monthly card volume across 5,000 transactions.
Under a blended 2.75 percent plus 10 cents, fees are $5,500 in percentage plus $500 in per-item, for $6,000 total. The effective rate is 3.0 percent. The merchant has no way to see how that splits.
Under IC++, assume true interchange averages 1.80 percent ($3,600), scheme and network fees average 0.14 percent ($280), and the negotiated markup is 0.25 percent plus 8 cents ($500 plus $400). Total is $4,780, an effective rate of 2.39 percent. The merchant saved about $1,220 that month, and every dollar of it was processor margin that blended pricing had hidden.
The savings are not guaranteed and they are not free. IC++ statements are longer, the rate moves with card mix, and reading them takes effort. But the merchant can now see the true cost, which means the markup is the only variable left to argue about.
Takeaway
The merchant discount rate is three stacked layers, and only one of them, the acquirer markup, is actually negotiable. Blended pricing hides which layer is which; interchange-plus-plus exposes all three. The discipline that pays for itself is dividing total fees by total volume every month to get the real effective rate, then reading the line items closely enough to catch downgrades. A merchant who cannot see the cost stack cannot manage it, and the pricing model that keeps it invisible is rarely the one working in the merchant's favor.