Card Network
What Is a Card Network? Definition and How It Works
Definition
A card network is the payment infrastructure operated by companies such as Visa, Mastercard, American Express, and UnionPay that sets scheme rules, facilitates authorisation message routing between acquirers and issuers, and manages clearing and settlement between member institutions.
How it works
Card networks operate the rails that connect the merchant's acquiring bank to the cardholder's issuing bank. When an authorisation request leaves the acquirer, it travels over the card network's messaging infrastructure to the issuing bank, which approves or declines the transaction and returns its response via the same network.
Networks publish and enforce scheme rules, the rulebooks that govern how members (acquirers, issuers, processors) must behave. These rules define everything from chargeback time limits and fraud liability allocation to acceptable merchant category codes and retry policies. Violating scheme rules results in fines assessed against the acquirer, who typically passes them to the merchant.
Card networks also set interchange rates, the per-transaction fees paid by acquirers to issuers on each approved transaction. These rates are published in scheme fee schedules and updated on a regular cadence (typically twice annually for Visa and Mastercard in the US).
Visa and Mastercard operate as four-party networks: merchant, acquirer, network, issuer. American Express and UnionPay historically operated as three-party networks where they act as both network and issuer, though both now also support third-party issuing.
Why it matters
Scheme rules are non-negotiable and enforced by the network, not the acquirer: merchants are ultimately bound by Visa and Mastercard rules regardless of what their acquirer contract says. Violations surface as scheme fines charged back through the acquirer.
Chargeback thresholds are set by card networks: Visa and Mastercard each publish monitoring programs with chargeback ratio thresholds that trigger escalating consequences. Merchants cannot negotiate these thresholds.
Network fees are a distinct cost line from interchange: scheme fees cover authorisation, clearing, and cross-border processing charges. They are non-negotiable but can be reduced through transaction data quality improvements (Level 2/3 data) and acceptance method optimisation.
Network connectivity affects approval rates: authorisation requests that fail to reach the issuer due to network routing issues register as declines. Merchants with multi-acquirer setups connected via different network paths reduce exposure to single-network outages.
With PXP
PXP maintains direct connections to Visa, Mastercard, and other card networks, enabling authorisation message routing without intermediary hops. PXP's platform handles scheme rule compliance monitoring and surfaces network-level decline codes to merchants for granular decline analysis.
Frequently asked questions
What's the difference between a card network and a payment processor?
A card network operates the messaging rails and sets the rules that all participants must follow. A payment processor handles the technical routing of transaction data on behalf of an acquirer, using the network's rails. The network sets the framework; the processor operates within it on the acquirer's behalf.
How do card networks differ from each other?
Visa and Mastercard are open-loop networks that licence their rails to banks for issuing and acquiring. American Express has historically operated as a closed-loop network acting as both network and issuer, though it now supports third-party issuing too. UnionPay is the dominant network in China. Networks differ in market coverage, interchange rate structures, scheme rules, and fraud liability policies.
How do card network rules affect merchants?
Scheme rules govern chargeback rights and time limits, retry policies after declines, 3DS authentication requirements, and acceptable business categories. Merchants who breach these rules face fines assessed through their acquirer. The rules are updated periodically, and merchants are responsible for staying compliant even when changes are not communicated directly.
Do card networks ever communicate directly with merchants?
Generally, no. Card networks communicate through acquirers, who are responsible for ensuring their merchants comply with scheme rules. However, networks do operate merchant-facing registration programs, such as Visa's Merchant Purchase Inquiry and Mastercard's Merchant Registration Program for high-risk categories, where direct registration is required.
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