What happens when you swipe or tap a credit card
When you hand over a credit card at checkout, a chain of four separate organisations springs into motion in seconds. The merchant's terminal reads your card number and sends it to an acquiring bank (the merchant's bank). That bank forwards the request to your card network — Visa, Mastercard, American Express, or Discover. The network routes it to your issuing bank (the bank that issued your card). Your bank checks whether you have available credit and whether the transaction looks fraudulent, then sends back an approval or decline. The whole cycle takes less than a second.
The physical card itself is just a key. The real transaction happens in the banking system behind it. Your card number, expiration date, and the three-digit security code on the back are the only information needed. The merchant never sees your name, address, or PIN unless you provide them separately.
Key Takeaways
- Four parties handle every transaction: your issuing bank, the card network, the acquiring bank, and the merchant, each taking a small cut.
- The merchant pays a processing fee (typically 1.5% to 3.5% of the sale) that is split among the network, the acquiring bank, and the card issuer.
- Settlement — when money actually moves from your bank to the merchant's bank — happens one to three business days after the transaction, not when ready.
- Fraud detection happens in real time during authorisation, which is why some legitimate transactions are declined and why you may be asked to verify unusual purchases.
The four parties in every transaction
Your issuing bank is the bank that gave you the credit card. When a transaction request arrives, this bank decides whether to approve it based on your available credit limit and fraud rules. If you dispute a charge later, your issuing bank is the one that investigates and credits your account.
The card network — Visa, Mastercard, American Express, or Discover — owns the infrastructure that connects all the banks. It sets the rules for how transactions work, maintains the security standards, and collects fees from both sides. The network does not hold your money or the merchant's money; it is the middleman that makes the system work.
The acquiring bank is the merchant's bank. It maintains the merchant's account, deposits money into it after settlement, and handles chargebacks if a customer disputes a charge. The acquiring bank also provides the merchant with the terminal or software that reads the card.
The merchant is the business selling you something. They do not see your full card number after the transaction is complete, and they do not hold onto it. Payment processors and gateways (like Square, Stripe, or PayPal) often sit between the merchant and the acquiring bank, handling the technical side of accepting cards.
How the merchant pays for processing
The merchant does not pay a flat fee per transaction. Instead, they pay a percentage of the sale amount, usually between 1.5% and 3.5%, depending on the card type, the merchant's industry, and the acquiring bank's pricing. A $100 sale might cost the merchant $2 to $3.50 in processing fees.
This fee is split three ways. The interchange fee (typically the largest piece, around 1% to 2%) goes to your issuing bank as compensation for the risk of lending you money and for fraud losses. The assessment fee (a smaller percentage) goes to the card network. The remainder goes to the acquiring bank and any payment processor in the middle.
Different card types cost different amounts to process. A rewards card or a premium card often carries a higher interchange fee than a basic card, because the issuing bank has more risk or more cost. A debit card costs less to process than a credit card. This is why some merchants offer a discount for paying with debit or cash — they are passing along the savings.
Authorisation versus settlement
When you swipe your card, the transaction is authorised — the bank checks that the money is there and the transaction is not fraudulent, then holds that amount on your account. But the merchant does not receive the money yet. That happens during settlement, which occurs one to three business days later.
During those days, the merchant's acquiring bank batches up all the day's transactions and sends them through the network to the issuing banks. The issuing banks then move the money from customer accounts to the acquiring bank, which deposits it into the merchant's account. This delay is why a refund you request today may not show up in your account until three to five business days later — the money has to travel back through the same chain.
The hold on your account during authorisation is temporary. If the merchant never settles the transaction (for example, if they go out of business or if the system fails), the hold drops off after a few days and the money is released back to you. This is different from a completed charge, which is permanent until you dispute it.
How fraud detection works in real time
Your issuing bank runs every transaction through fraud detection rules in milliseconds. These rules look for patterns: a purchase in a different country minutes after a purchase at home, a purchase far above your normal spending, a purchase at a merchant type you never use, or a purchase that matches known fraud patterns.
If a transaction looks suspicious, the bank can decline it outright, or it can send a verification request to your phone or email asking you to confirm the purchase. Some banks use a code sent via text message; others use a push notification to a banking app. This is called two-factor authentication or strong customer authentication.
Fraud detection is why some legitimate purchases are declined — the rules are conservative to protect you, and they sometimes flag legitimate transactions by mistake. If this happens, you can call your bank to confirm the purchase, and the bank will adjust its rules for future transactions from that merchant.
What happens when you dispute a charge
If you see a charge you did not make, you contact your issuing bank and file a dispute. The bank then contacts the acquiring bank and asks for proof that you authorised the transaction. The merchant has a window (usually 10 to 30 days, depending on the card network) to provide evidence — a signed receipt, a shipping confirmation, or a video of you entering your PIN.
If the merchant cannot provide evidence, the bank credits your account and the merchant loses the money. If the merchant provides strong evidence, the bank sides with the merchant and you keep the charge. During the dispute period, the amount is usually credited to your account temporarily while the investigation happens.
This dispute process is why merchants are careful about keeping records and why some merchants ask for a signature or ID — it is evidence that you were present and consented to the transaction. Online merchants keep email confirmations and IP addresses for the same reason.
Why some merchants do not accept all card types
A merchant might refuse American Express or Discover because the interchange fees are higher than Visa or Mastercard. A small business operating on thin margins might not be able to absorb a 3% fee on every sale, so they steer customers toward cheaper payment methods.
Some merchants also refuse cards because of the chargeback rate — if a merchant has too many disputes, the card networks can raise their fees or drop them entirely. A merchant with a high chargeback rate might refuse to accept cards online, or might require a signature in person.
Merchants can also refuse a specific card if they have had fraud problems with that card type or if their acquiring bank has restrictions. This is rare, but it happens when a card network or issuing bank has had security breaches or when a merchant's fraud losses spike.
Frequently Asked Questions
Why does it take three days for money to show up in a merchant's account?
Settlement requires the acquiring bank to batch transactions, send them through the card network to each issuing bank, and then move the money back. Each step takes time, and banks process these batches once per day, usually overnight. A transaction approved on Monday might not settle until Wednesday or Thursday.
Can a merchant see my full credit card number after I pay?
No. Payment processors and card networks are designed so the merchant never stores your full card number. The merchant sees only the last four digits and the card type. This protects you if the merchant's system is hacked — the thief cannot steal your full card number because the merchant never had it.
What is a payment gateway and how does it fit in?
A payment gateway (like Stripe, Square, or PayPal) is software that sits between the merchant and the acquiring bank. It encrypts your card information, routes the transaction to the right network, and handles the technical details. The merchant pays the gateway a fee, which is part of the overall processing cost.
Why do some transactions ask for a CVV but others do not?
The three-digit CVV (card verification value) on the back of your card proves you have the physical card in your hand. In-person transactions do not need it because the merchant can see the card. Online transactions require it because the merchant cannot verify you have the card. Some merchants skip it if they have other ways to verify you, like a saved payment method or a loyalty account.
What happens if I use a stolen card?
The fraud detection system usually catches it within seconds and declines the transaction. If it does not, the real cardholder will dispute the charge, and the merchant will lose the money during the chargeback process. The merchant may also be liable for the chargeback fee itself, which can be $15 to $100 per dispute.