Every time a consumer taps their card at a terminal, a carefully orchestrated exchange takes place between four distinct parties. Understanding this model is essential for anyone working in payments - it determines how money flows, who bears risk, and why interchange fees exist.
The Four Parties
Cardholder - The consumer holding the payment card. They have a contractual relationship with their issuing bank.
Merchant - The business accepting the card payment. They have a contractual relationship with their acquiring bank.
Issuer (Issuing Bank) - The bank that issued the card to the consumer. They extend credit (credit cards) or provide access to funds (debit cards), set spending limits, handle fraud screening, and bear the risk of cardholder default. Examples: Chase, Barclays, DNB.
Acquirer (Acquiring Bank) - The bank or payment institution that processes card payments on behalf of the merchant. They maintain the merchant relationship, provide the terminal or payment gateway, and settle funds to the merchant's account. Examples: Worldpay, Adyen, Stripe, Nexi.
The Scheme's Role
Visa and Mastercard sit in the middle - they don't issue cards and they don't acquire merchants. They operate the network that connects issuers and acquirers, set the rules, and route transactions. This is why it's called the "four-party" model, even though the scheme is a fifth participant.
How Money Flows
When a cardholder makes a €100 purchase:
The issuer debits €100 from the cardholder's account; The issuer pays the acquirer €100 minus the interchange fee (e.g., €99.70); The acquirer pays the merchant €100 minus the merchant discount rate (e.g., €99.00). The merchant discount rate (MDR) typically comprises three components: interchange (paid to issuer), scheme fee (paid to Visa/MC), and acquirer markup (retained by acquirer). Interchange is by far the largest component, typically 0.2–0.3% for debit cards and 0.3–1.5% for credit cards in the EU (capped by the Interchange Fee Regulation).
Three-Party vs Four-Party
American Express and Discover traditionally operate a three-party model - they are both the issuer and the acquirer. This gives them direct relationships with both cardholders and merchants, more control over pricing, but also more balance sheet risk. Amex has increasingly moved toward a hybrid model, licensing third-party banks to issue Amex cards.
Why Co-Badging Matters
In Europe, the Interchange Fee Regulation (IFR) requires that debit cards can carry multiple scheme logos - for example, a German girocard co-badged with Visa, or a Norwegian BankAxept card co-badged with Mastercard. At the point of sale, the terminal or cardholder may choose which scheme processes the transaction. This promotes competition and can reduce costs for merchants.
Co-badging is a key battleground: domestic schemes (girocard, BankAxept, Dankort, Cartes Bancaires) compete with Visa and Mastercard for transaction routing, particularly for in-store debit purchases.
Key Takeaway
The four-party model creates a marketplace dynamic: issuers compete for cardholders, acquirers compete for merchants, and schemes compete for routing volume. Understanding these incentives is fundamental to understanding card payment economics.