Assessment fees vs
interchange vs markup:
the three layers, separated

Ask most merchants what their processing rate is and they'll give you one number. That number is never one fee — it's three fees from three different companies, stacked on top of each other and usually presented as if they were a single charge from "the processor." Knowing where the line falls between them is the difference between negotiating the 20-30% of your rate that's actually negotiable, and wasting time trying to talk down a number your processor has no authority to change.

Layer one: interchange, paid to the issuing bank

Interchange is the fee paid to the bank that issued the cardholder's card — Chase, Bank of America, Capital One, whichever institution mails the physical card and extends the credit line or holds the deposit account. It is set by Visa and Mastercard on published schedules, but the money itself flows to the issuer, not the network. Interchange varies by card type (debit vs. credit, rewards vs. non-rewards, consumer vs. commercial), by merchant category code, and by how the transaction was processed — card-present and chip/tap transactions generally qualify for lower rates than manually keyed or card-not-present sales, which is the mechanic behind downgrades when a transaction misses its category's requirements.

Interchange is also where the Durbin Amendment draws its hardest line: regulated debit interchange from large banks is capped, while credit interchange is not, which is why MidPay's locked benchmark figures — 1.49% on debit and 2.69% on credit — sit so far apart. That spread is not a MidPay markup decision; it reflects a structurally different interchange category underneath each card type. Published third-party breakdowns of total processing cost commonly attribute roughly 70% of the total to interchange, making it by far the largest of the three layers.

Layer two: the network assessment fee

The assessment fee is paid directly to the card network — Visa or Mastercard — not to the issuing bank. It funds the actual infrastructure: the authorization and settlement rails, the fraud and dispute systems, the brand itself. Unlike interchange, which varies widely by card category, the assessment fee is a small, close-to-flat percentage applied to nearly every transaction regardless of card type. As of 2026, published rate breakdowns put Visa's assessment fee at roughly 0.14% on credit transactions and 0.13% on debit, with Mastercard close behind at roughly 0.1375% on credit and 0.13% on debit — figures that shift only slightly and infrequently when the networks adjust their published schedules. Network-level breakdowns commonly attribute around 10% of total processing cost to assessments and related dues.

On top of the core assessment, the networks also charge a handful of smaller, itemized fees that ride alongside it — a network access/data usage fee on some processors' statements, cross-border fees on international cards, and card-brand-specific line items like Mastercard's separate fee for manually keyed (MOTO) authorizations. None of these are set by your processor. They are published, uniform, and identical no matter which acquirer routes your transactions.

Interchange and assessment are the two layers nobody can negotiate — not your processor, not you, not anyone. The only layer up for discussion is what gets added on top.

Layer three: processor markup — the only negotiable part

Markup is the margin your processor or acquirer adds on top of interchange and assessment to cover its own cost of doing business — underwriting, risk, support, the merchant account infrastructure, and its own profit. This is the only one of the three layers that varies by who you process with, and the only one where negotiation actually changes what you pay. Under interchange-plus pricing, markup is disclosed as its own line — typically a small percentage (a few basis points to a fraction of a percent) plus a flat per-transaction fee, itemized separately from interchange and assessment on the statement.

Under flat-rate or tiered pricing, this same markup exists — it has to, or the processor makes no money — but it's blended invisibly into a single published rate, like a flat 2.6% + 10¢ per transaction. That flat number has to cover the processor's true cost across every card that comes through, including the expensive ones, which means on a merchant with a favorable card mix (more debit, fewer rewards cards), the blended flat rate is quietly absorbing a larger effective markup than an itemized interchange-plus statement would ever show in daylight.

Why this split matters more than the headline rate

A merchant comparing two processing offers who only looks at the final blended percentage is comparing three unequal things without knowing it: two fixed, non-negotiable network costs, and one negotiable margin. A quote that looks 0.3 points cheaper could be quietly assuming a different card mix, or absorbing interchange downgrades into its "flat" number in a way that costs more once your actual transactions run through it. The only way to compare offers honestly is to separate all three layers and compare markup to markup — which is exactly what an itemized interchange-plus statement lets you do and a blended flat-rate quote does not.

This is also why "we'll beat any rate" offers deserve scrutiny rather than excitement. Interchange and assessment set a floor no processor can go below without operating at a loss. If a competing quote's total is below what interchange and assessment alone would cost on your actual card mix, either the quote is not itemized honestly, or it is a promotional rate that reverts once you've switched. Ask any processor to show interchange, assessment, and markup as three separate lines before comparing a single blended number.

What to actually do with this

1. Ask for an itemized interchange-plus statement, not a blended rate — it's the only format that shows all three layers separately.
2. Compare markup to markup across quotes, not total percentage to total percentage — the networks' share is fixed regardless of who you sign with.
3. Treat any offer below your real interchange-plus-assessment floor as a red flag, not a win — verify what happens after any introductory period.
4. Re-check your card mix against your assumed interchange blend at least quarterly — a shift toward more rewards or commercial cards raises the interchange layer regardless of what your processor charges.

Frequently asked questions

What is the difference between interchange and assessment fees?

Interchange is paid to the cardholder's issuing bank and varies by card type, merchant category, and how the transaction was processed. The assessment fee is paid to the card network itself (Visa or Mastercard) and is a small, flat percentage applied uniformly regardless of card type — currently around 0.13-0.14% of the transaction on both networks. Interchange funds the issuer's rewards and risk; the assessment funds the network's rails, brand, and fraud systems.

Can a merchant negotiate interchange or assessment fees?

No. Both interchange and network assessment fees are set by Visa and Mastercard and published on fixed schedules that apply to every acquirer and processor identically. Nothing about your processor relationship changes what you pay for these two layers — they are pass-through costs. The only negotiable layer is the processor's markup on top of them.

What is processor markup and how much should it be?

Markup is the margin a processor or acquirer adds on top of interchange and assessment to cover its own operating cost and profit. Under interchange-plus pricing, markup is disclosed as a separate line — commonly a fraction of a percent plus a small per-transaction fee. Under flat-rate or tiered pricing, markup is blended invisibly into a single rate, which is why a flat 2.6%+10c model can cost more than interchange-plus even at a lower headline number, depending on card mix.

Why does my statement only show one percentage instead of three?

Because most pricing models blend all three layers into one number by design. Flat-rate and tiered pricing report a single rate per card category, which hides how much of it is interchange, how much is assessment, and how much is processor margin. Only interchange-plus (and true cost-plus) statements itemize the three layers separately, which is the only way to see what you are actually paying for versus what your processor is keeping.