A card payment is a stack, not a vendor. The cardholder, the merchant, the issuing bank, the card network, the acquirer, a processor, an ISO, and often a software vendor (an ISV) each do a different job on the same sale. The logo on the terminal is usually one of those layers, not all of them. Name the layers and a statement stops looking like a single "processing rate" and starts looking like what it is: interchange to the issuer, assessments to the network, and markup to whoever sold and serviced the account.
That stack is how most U.S. commerce actually moves. In 2024, cards were 79 percent of U.S. noncash payments by number and only 8 percent by value, according to the Federal Reserve Payments Study released 1 Jul 2026. Debit ran 120.6 billion payments. Credit ran 67.1 billion, and grew faster than debit for the first measured three-year period since 2000. ACH carried $104.06 trillion, 74 percent of noncash value. Cards dominate the register. Large payments still go by ACH.
The five names people collapse into "my processor"
Networks. Visa, Mastercard, Discover, and American Express write the brand rules and publish interchange schedules. They are not your merchant account. They do not deposit money to your bank. They sit in the middle of the four-party model (cardholder, issuer, merchant, acquirer) and take assessments, network dues, on volume. You do not negotiate with a network. Your customers bring the brand. You accept it.
Acquirers. The acquirer is the bank-side network member that sponsors the merchant ID (MID) and is the party the brands can hold liable. In speech, "acquirer" and "processor" get used as synonyms. They are not. The acquirer is the member. The processor is the engine.
Processors. The processor authorizes, captures, and settles. It talks to the networks, posts the batch, and instructs funding. When a statement says "processing," this is the switching and settlement work. Many contracts bundle processor and acquirer under one brand, which is why the two words collapse in a sales conversation.
ISOs. An Independent Sales Organization originates and supports merchants for a registered acquirer or ISO/MSP. The ISO usually does not hold the money. It sells, boards, and services. If you have a named agent, a "rep," or a local merchant-services office, that is this layer. What it earns is a residual of markup, never of interchange or assessments.
ISVs. An Independent Software Vendor is the POS, invoicing, scheduling, or checkout product that captured the card. Software can sit in front of any processor. It can be a referral, a gateway integration, or a deeper embedded relationship. The software is not the bank. If you sell or buy that layer, the map is in embedded payments.
Visa, Mastercard, Discover, American Express. They set interchange, assessments, and brand rules.
The bank-side network member that sponsors the merchant ID and is liable to the brands.
The engine that authorizes, captures, and settles. Often branded as your processor even when it is not the acquirer.
The sales and service organization that boarded you. Markup, not interchange, is what it lives on.
A payment gateway is a thinner slice still: the pipe that carries the authorization request. It is not the acquirer and it is not, by itself, a merchant account.
How one sale actually moves
Take a card-present sale. The path is the same whether the ticket is $12 or $1,200.
- The customer presents a card. The ISV or terminal builds an authorization request.
- The processor sends that request to the card network.
- The network routes it to the issuing bank, the bank that gave the customer the card.
- The issuer approves or declines against the cardholder's credit or deposit account.
- The answer travels back the same path in a few seconds. That is authorization, not money in your account.
- Later, usually when you close or auto-close a batch, the processor captures the authorized amount and submits it for settlement.
- Settlement is when the networks move value: the issuer pays, the acquirer receives, and the merchant's bank is funded, minus the fees the contract allows to be withheld.
Authorization is a yes. Capture is a claim. Settlement is the money. Tips, delayed capture, voids, and refunds live in the gaps between those clocks. None of that requires you to have a direct contract with Visa.
American Express (and, historically, Discover) can look like a shorter stack because the brand may be issuer and network at once. The merchant still has an acquirer or processor in front of that brand. The names change. The jobs do not.
A payment facilitator is a different shape of the same stack: you sit as a sub-merchant under someone else's master account instead of holding your own MID. Boarding is usually faster. Switching cost and who owns the relationship live in that difference. It does not remove networks, issuers, or interchange.
Why the statement has fifty lines
Every card fee you pay is still one of three things, no matter how many logos are on the hardware.
- Interchange goes to the issuing bank. Networks set it. No ISO discounts it.
- Assessments go to the networks. Small. Pass-through. Also not negotiable.
- Markup is everything else: the processor's and ISO's margin, plus monthly extras that are not on a network schedule. This is the only layer a buyer can actually compete on.
The three-layer walkthrough is interchange vs assessments vs markup. Pricing models (interchange-plus, tiered, flat-rate, surcharge, dual pricing, and interchange optimization) are just different ways of packaging those layers. The stack underneath does not change when the quote does.
The Federal Reserve counted 236.6 billion noncash payments in 2024, totaling $140.01 trillion. If your mix is debit-heavy and card-present, interchange is doing less of the work. If it is rewards credit and keyed or e-commerce, interchange is doing more. Either way, the processor did not invent that floor. Mix is why two merchants on the same markup show different effective rates.
Who you actually have a contract with
Read the merchant agreement for three names:
- The registered ISO/MSP or sales organization (who boarded you).
- The processor (who switches the transactions).
- The acquiring bank (who is the network member).
If the agreement is silent, ask. The receipt and the terminal firmware will show a network brand and sometimes a processor or POS name. That is not a complete map. When software "includes payments," ask who the acquirer is and whether you own the MID. The vendor is a stack. The statement is the bill for that stack.
When a quote names a single rate, ask which layer it is talking about. When a statement has fifty lines, sort them into issuer, network, and markup. The practical next page for that sorting is how to read your merchant statement.
FAQ
How does credit card processing work? The merchant's software or terminal sends an authorization to a processor, which routes it through a card network to the issuing bank. If the issuer approves, the sale is later captured and settled to the acquirer, then funded to the merchant, minus interchange, assessments, and markup.
What is the difference between an acquirer and a processor? The acquirer is the bank-side network member that sponsors the merchant ID and is liable to the brands. The processor is the engine that authorizes, captures, and settles. Contracts often bundle the two under one brand, which is why the words get used as synonyms.
What is an ISO in credit card processing? An Independent Sales Organization originates and supports merchants for a registered acquirer or ISO/MSP. It usually does not hold the funds. It sells, boards, and services, and it is paid from markup, not from interchange or assessments.
What is an ISV in payments? An Independent Software Vendor is the POS, invoicing, scheduling, or checkout product that captured the card. Software can sit in front of any processor. It is not the bank, not the network, and not a substitute for reading who actually holds the merchant account.
Do I have a contract with Visa or Mastercard? Almost never directly. You contract with an ISO, processor, acquirer, or payment facilitator. The networks set brand rules and interchange schedules that those parties must follow. The logo on the terminal is the brand the customer brought, not your counterparty.
Why do cards dominate payments by number but not by value? Cards are how most small purchases clear at the register. In 2024 they were 79 percent of U.S. noncash payments by number and 8 percent by value (Federal Reserve FRPS, released 1 Jul 2026). Large-dollar transfers still run on ACH, which carried $104.06 trillion, 74 percent of noncash value.
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