How does a card scheme work?
The scheme sets the rules, and banks issue cards and acquire merchants under them. The EU Interchange Fee Regulation defines a payment card scheme as a single set of rules, practices and standards for card payments, separate from the infrastructure that processes them. In a four-party scheme, a payment moves from the payer’s account to the payee’s account through the scheme, an issuer on the payer’s side and an acquirer on the payee’s side. In a three-party scheme, the scheme itself issues and acquires. The regulation treats a three-party scheme as four-party once it licenses other providers to issue or acquire.
Why does it matter?
Scheme rules shape much of what a merchant can do: how disputes run, what data an authorization carries, which retries are allowed. Schemes also set the structure of costs. Visa’s interchange schedule describes interchange as transfer fees between financial institutions and says it is a supplement to the Visa Core Rules, which govern in any conflict. As an illustrative example: on a 100 euro card order, a merchant pays 1.80 euros in total, of which 0.30 euros is interchange to the issuer, 0.15 euros is scheme fees and 1.35 euros is the acquirer’s and provider’s margin.
What are the limits?
Acceptance differs by brand and market. Stripe’s documentation lists global networks such as Visa, Mastercard, American Express, UnionPay and JCB alongside local networks such as Cartes Bancaires in France and eftpos in Australia, each with its own supported countries and features. A brand accepted on paper can still fail if the acquirer behind a route does not support it.
Where does Omno use it?
Omno does not acquire and is not a scheme member. It connects to PSPs, which work with acquirers connected to the schemes. Card attributes such as issuing country can be routing conditions, so card traffic can go to the provider that accepts it best, and the routing-decision log records the response code for every attempt.