Card NetworksWhat They Are, How They Work, and Why They Matter for Merchant Operations

What is a Credit Card Network? Why Are Card Networks Necessary? 

Okay. Imagine that you’re someone who has never used a credit card in your life. I know that’s a pretty farfetched prospect at this point, but stay with me for a moment.

Even if this was the case, you’d probably still be familiar with at least one or two card networks. Brand names like Visa and Mastercard are an integrated part of our culture at this point. Even if you had never used a Visa-branded card before, you’d probably still be aware of the Visa brand name.

But, have you wondered exactly what those companies do? Their logos appear on billions of circulating payment cards, but they’re not banks or card sponsors (at least, not in most cases). So, why are their logos there? What’s the difference between a card network and a bank?

In this post, I’m going to help you understand the essential role that card networks play in the payment process. I’ll talk about all the different stakeholders, how they interact with each other, and how that interplay is an essential part of every card transaction.

What is a Card Network?

A card network — also called a “card scheme” or “card association,” depending on the region in question — is the infrastructure that enables card-based payments. Major card networks include Visa, Mastercard, American Express, and Discover.

The card networks connect the parties involved in every transaction: the cardholder, the merchant, the issuing bank, and the acquiring bank. They provide the technology, rules, and standards that allow a card issued by one bank to be accepted by a merchant using an entirely different bank.

Without card networks, each bank would need direct relationships with every merchant. It would be an impossible scale problem that would make card acceptance totally impractical.

The Role of Card Networks in Payment Processing

Every card transaction involves multiple parties. The card network sits at the center, connecting them all.

The card network develops and enforces network rules that all parties must follow during the transaction process. These rules are outlined in a core rules document, which each brand updates periodically.

Networks regulate virtually every aspect of card acceptance. They define:

• How cards can be accepted, authorized, and settled.
• Security requirements including PCI DSS compliance, encryption standards, and tokenization practices.
• Authentication protocols like 3D Secure and determine when liability shifts from merchant to issuer.
• How and when refunds must be processed.
• Chargeback procedures, including how disputes are filed, what evidence merchants can submit, and how outcomes are determined.
• Which activities are prohibited, like improper surcharging or setting minimum purchase amounts above allowed thresholds.

Setting the rules for how transactions get conducted on the network is just one responsibility that falls to the card networks, though. They end up playing multiple roles during the transaction process, including:

So, the card network is really essential at every step of the transaction process. They facilitate the actual settlement of funds between banks, but their involvement begins well before a transaction is ever initiated.

How Are Issuers Different from Card Networks?

The networks own the credit card system. However, it’s the network’s member banks that provide (issue) credit card accounts to consumers.

Banks and credit unions vet consumer applications, decide whether to offer that customer an account, and set a credit limit based on purchase and payment history. The cardholder may or may not have another account with that bank (other lines of credit, checking accounts, etc.).

When a bank issues a credit card to a consumer or business, they are essentially agreeing to loan the cardholder money on an ongoing basis. And, each time a card is dipped or swiped, the issuer decides whether or not to approve the purchase. With debit, the card is tied to funds that are already deposited into an account in the cardholder’s name.

In contrast, payment networks are like a communications hub for the transaction process. They control and maintain the overall framework that connects banks and merchants. Networks also decide which banks can issue their cards.

Each card brand has a “network” of specific merchants; these are the only retailers allowed to accept payments on that organization's behalf. Retailers must be approved by the card network in order to accept that brand of card. In other words, a consumer cannot pay via Mastercard unless the merchant is in the Mastercard network.

Consequences for Noncompliance With Card Network Rules

Card networks actively monitor merchant activity for rule violations. Your processor and acquiring bank are responsible for ensuring you comply, and they’ll take action if you create risk for them.

Violations can trigger fines, higher processing fees, mandatory monitoring programs, and more scrutiny of your transactions. You could even lose the ability to accept that network’s cards entirely. Realistically, though, your processor is likely to freeze or terminate your account well before it even gets to that point.

Key compliance areas for merchants include (but are not limited to):

• Displaying network marks correctly
• Honoring all cards within a network’s family without cherry-picking
• Processing refunds within required timeframes
• Following security requirements for both card-present and card-not-present transactions
• Meeting data security standards

Each network publishes its own detailed rulebook—Visa Core Rules, Mastercard Rules, and so on. Your acquirer and processor can help you interpret these requirements, but ultimate responsibility for compliance lies with you.

Card Network Chargeback Rules

I touched on card network compliance in the last section. But, probably the single most problematic area of compliance for most merchants is as it regards chargebacks, or payment disputes.

When a cardholder disputes a transaction, the card network’s rules determine how that dispute is processed. Networks define everything from the reason codes used to categorize disputes to the evidence required to fight them.

Each network establishes its own framework for disputes. They define how chargeback reason codes get used. They set time limits for how long cardholders have to dispute a transaction and how long merchants have to respond. They specify what documentation qualifies as “compelling evidence” for each dispute type. And, they determine liability rules based on how the transaction was processed; for example, whether 3D Secure was used.

Visa and Mastercard have similar but not identical dispute processes, with different terminology, timelines, and evidence requirements. Discover and American Express handle disputes differently, too, because they serve as both networks and issuers. Response windows, escalation paths, and win rates vary across networks.

Networks also run monitoring programs that track merchant dispute and fraud rates. Exceeding established thresholds triggers escalating consequences. The Visa Acquirer Monitoring Program monitors combined fraud and dispute rates, with fines and potential termination for merchants who exceed thresholds. Mastercard has their own programs for monitoring fraud and chargebacks, each with similar consequences.

Card Network Fees for Merchants

As you know, you’ve got to pay a fee for every transaction you process, averaging somewhere between 1.5% to 3.5% per transaction. We can break this fee down into three components: interchange, assessment fees, and processor markup.

The card network plays a central role in determining how much you’re ultimately going to end up paying. While they don’t have any influence over your processor markup (that’s between you and your processor), they have direct control over how much you pay in interchange and assessment fees.

Open & Closed Card Networks: What’s the Difference?

Card networks operate under two distinct models: an “open” or a “closed” model.

For merchants, this distinction has practical implications. Open networks offer wider card acceptance because more banks issue cards on them, meaning more cardholders carry those cards.

Closed networks may have different fee structures. American Express, for example, historically charged higher merchant fees than Visa or Mastercard, which is why some merchants choose not to accept it. Dispute processes also differ; dealing directly with Amex can be simpler in some ways, but offers less separation between the network setting rules and the issuer making decisions.

Comparing the Major Card Networks

So, how do the four major brands active in the US market stack up? Here’s a quick comparison of the major players and what distinguishes them:

Network	Model	Market Share (by Purchase Volume)	Purchase Volume (in $USD)	Key Merchant Considerations
Visa	Open	52.2%	$3.2T	Largest acceptance; VAMP monitoring program
Mastercard	Open	24.9%	$1.52T	Similar to Visa; ECM/EFM/SMMP programs
Amex	Closed	19.5%	$1.19T	Higher fees; direct merchant relationships; some merchants don’t accept
Discover	Closed	3.5%	$212B	Lower fees than Amex; growing acceptance

As you can see, Visa holds roughly half of US card transaction volume, making it the most important network for most merchants to understand. Mastercard operates similarly to Visa in most respects, with comparable interchange structures and dispute processes, though the specific rules and monitoring programs differ.

American Express commands premium interchange rates but serves a cardholder base with higher average spending. Discover offers competitive rates and has expanded acceptance significantly, though it still trails the larger networks in transaction volume.

A Final Word on Card Networks

Understanding the role credit cards networks play in facilitating payments can give both merchants and consumers a better view of how the entire process works, end to end. That information can help cardholders make decisions that will minimize fees and optimize benefits.

Knowing how the credit card system works, however, won’t always protect from inherent dangers such as fraud.

At Chargebacks911®, we specialize in helping merchants mitigate fraud risk and other potential credit card threats. If you’d like to know how we can help your business, contact us today.