The Payments Stack Explained
Every time a customer pays with a card, the transaction passes through multiple layers of technology and financial institutions. Here's how the entire stack works, from the cardholder's tap to the funds landing in the merchant's account.
How a Transaction Flows
A card transaction goes through two main phases: authorization (real-time, ~1-2 seconds) and settlement(batch process, typically end-of-day). Here's every entity involved:
Cardholder
The customer who initiates a payment using their credit or debit card.
The cardholder is the consumer or business that holds a payment card issued by their bank. When they swipe, tap, dip, or enter their card number online, they kick off a complex chain of events that typically completes in under 2 seconds.
Merchant
The business accepting the payment for goods or services.
Merchants range from a solo Etsy shop to a Fortune 500 retailer. To accept card payments, they need a merchant account (or use a payment facilitator like Stripe or Square). The merchant's choice of processor, gateway, and acquiring bank directly impacts their per-transaction costs.
Payment Gateway
The technology that securely transmits transaction data from the merchant to the processor.
Think of the gateway as the digital equivalent of a physical card terminal. For online transactions, the gateway encrypts the cardholder's data and routes it to the payment processor. Popular gateways include Stripe, Braintree, and Authorize.Net. Some processors bundle the gateway into their offering, while others require you to choose a separate gateway provider.
Payment Processor
Routes transaction data between the merchant's bank and the cardholder's bank.
The processor is the central nervous system. It receives the transaction request from the gateway, communicates with the card network to authorize the transaction, and then handles the settlement process. Front-end processors handle authorization; back-end processors handle settlement. Major processors include Fiserv (First Data), Worldpay, TSYS, and Global Payments.
Card Network
Sets interchange rates, rules, and facilitates communication between banks.
Visa, Mastercard, American Express, and Discover are the four major card networks in the US. They don't issue cards or hold accounts — they operate the infrastructure that connects issuing banks to acquiring banks. They set interchange fee schedules (hundreds of rate categories), establish security standards (like EMV), and arbitrate disputes. Visa and Mastercard are open networks (work with any issuing/acquiring bank), while Amex and Discover traditionally operate as closed networks.
Issuing Bank
The cardholder's bank that issued the credit or debit card.
The issuing bank (or issuer) extends credit to the cardholder and is responsible for paying the acquiring bank during settlement. They evaluate the authorization request — checking available credit, fraud signals, and account standing. They earn the majority of the interchange fee. Major issuers include Chase, Bank of America, Citi, Capital One, and American Express (which is both a network and issuer).
Acquiring Bank
The merchant's bank that receives funds from the issuing bank.
Also called the acquirer or merchant bank, this institution holds the merchant's account and receives settlement funds on their behalf. The acquirer assumes risk — if a merchant can't fulfill chargebacks, the acquirer is on the hook. Many processors have acquiring relationships or are acquirers themselves. The acquirer deducts fees (interchange + assessments + their markup) before depositing net proceeds into the merchant's account.
The Transaction Lifecycle
Phase 1: Authorization (Real-Time)
- Customer initiates payment — swipe, dip, tap, or enter card online
- Merchant's gateway/terminal encrypts card data and sends to the payment processor
- Processor routes the authorization request through the card network (Visa/MC) to the issuing bank
- Issuing bank evaluates — checks credit limit, fraud signals, account status
- Approval or decline response travels back through the same chain to the merchant
Phase 2: Settlement (Batch)
- Merchant batches transactions at end of day and sends to the processor
- Processor submits the batch through the card network for settlement
- Issuing bank transfers funds (minus interchange fee) to the acquiring bank via the card network
- Acquiring bank deposits the net amount (minus markup and assessment fees) into the merchant's account
Where Do the Fees Go?
A typical 2.9% + $0.30 fee on a $100 transaction breaks down roughly like this:
| Recipient | Fee Component | Typical Amount |
|---|---|---|
| Issuing Bank | Interchange fee | ~$1.75 (1.75%) |
| Card Network | Assessment/network fee | ~$0.14 (0.14%) |
| Processor/Acquirer | Markup | ~$1.31 (remainder) |
Note: These are illustrative. Actual interchange rates vary by card type, merchant category, and transaction method.
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