Card scheme

What a card scheme does

A card scheme is the network and rulebook that makes card payments interoperable. Visa, Mastercard, American Express and Diners Club each operate one: the infrastructure that routes authorisation messages between thousands of issuers and acquirers, the clearing and settlement machinery that moves the money, and the rules that govern everything from interchange and chargebacks to security standards and branding. When a card and a checkout that have never met complete a payment in two seconds, the scheme is what made it possible.

Four-party and three-party models

Visa and Mastercard run four-party ("open loop") schemes: independent issuers and acquirers on either side, with the scheme as the network between them - which is why interchange exists, as the fee balancing the two sides. American Express and Diners Club historically run three-party ("closed loop") models, acting as issuer and acquirer themselves, which gives them direct relationships at both ends and different fee structures.

Schemes in a merchant's daily life

Merchants never contract with a scheme directly - the acquirer intermediates - but scheme rules shape daily reality: how long customers have to dispute a charge, how quickly an authorisation must be captured, how stored credentials must be flagged, and when 3-D Secure is required. Rule changes arrive several times a year, and keeping up is part of a payment provider's job. LekkaPay tracks scheme mandates and applies them in the gateway so merchants inherit compliance rather than chase it.