Card network is the scheme that connects issuing banks to acquiring banks, carries messages between them and writes the rules on what each party owes; Visa, Mastercard, American Express, Discover, JCB and UnionPay matter commercially. A network owns the switch and the rulebook, including dispute deadlines, data security standards and merchant category codes, but never holds merchant money, lends to cardholders or underwrites businesses. It sets interchange, paid to the issuer, and scheme fees, which it keeps; only the acquirer margin is negotiable. Membership demands capital and regulatory standing, so fintechs operate on a sponsor's license and BINs. Merchants crossing dispute or fraud ratio thresholds face escalating monthly fines and can lose the right to accept the brand.
How do card networks work
A network owns the switch and the rulebook. It never holds merchant money, never lends to a cardholder and never underwrites a business. It writes the dispute rules and deadlines, the data security standards and the merchant category codes, and it operates the switch that gets an authorization request to the right issuer.
Money and risk sit with the banks. When a payment fails or a fee changes, the first question worth asking is whether the cause is a scheme rule, an acquirer decision or a processing fault, because that determines who can actually fix it. The mechanics of one transaction moving through those parties are covered under card payment.
The fees a network sets, and where they go
Two of the three components of merchant pricing are set here. Interchange is defined by the network and paid to the issuer; scheme fees are defined by the network and kept by it. Neither is negotiable for a merchant of ordinary size. The third component, the acquirer margin, is the only line anyone bargains over.
Rate tables are granular: card type, merchant category, region, whether the card was present, whether authentication was applied. That is why the same basket can cost twice as much when paid with a commercial credit card issued on another continent.
Why access has to be rented
Submitting transactions into a network requires membership, and membership requires capital, reporting and regulatory standing that most payment companies do not have. Fintechs solve it through sponsorship: they sit on a principal member's license, use its BINs and scheme registrations, and accept its oversight. Losing a sponsor takes a business offline faster than any technical outage.
Enforcement and monitoring programs
Networks police behavior with thresholds. Cross a dispute or fraud ratio limit and the merchant enters a remediation program with escalating monthly fines, then loses the right to accept the brand. Acquirers enforce well ahead of that point, which is where reserves and volume caps on new accounts come from.
Where American Express is different
Visa and Mastercard run four-party schemes, sitting between separate issuers and acquirers. American Express historically issued and acquired itself, which let it set the merchant price end to end. Both now operate hybrid arrangements that license third parties, so the practical difference for a merchant is pricing and acceptance rather than structure.