A card payment is a transaction in which a customer authorizes their bank to pay a merchant with a credit, debit or prepaid card. What separates it from cash is that permission and money arrive at different moments: the approval comes back in about a second, the funds land days later.
How do card payments work
The card data is captured first, at a terminal or in a browser form. The merchant's acquirer then submits the request into the scheme, where routing and rulemaking belong to the card network rather than to either bank.
Third, the issuer approves or declines and reserves the amount against the account. Fourth, the merchant confirms the sale, which is a separate message — authorization and capture explains why the two are split. Fifth, the captured items go through clearing and the merchant is paid at settlement.
Where the flow breaks
Every stage fails differently. Data capture fails on expired cards and mistyped numbers. Authorization fails on limits, available funds and issuer fraud scoring, and the reason codes are not the same for a credit card as for a debit card — worth knowing before writing retry rules.
Capture fails silently. An approval that is never captured expires on its own within days, and the sale vanishes without anyone having declined it. Settlement itself rarely fails; it gets delayed.
Who is exposed, and when
Merchants asking what is card payment risk usually mean the window between approval and capture, and in that window nobody has lost anything, because the money is reserved rather than moved. Once the merchant captures, the position flips. The merchant has been paid and the cardholder has been billed, so every later problem is resolved by pulling money back out of the merchant through the dispute flow.
That asymmetry explains acquirer behavior across the board. A business that captures on order and ships three weeks later is holding money it may have to give back, and its acquirer prices and reserves accordingly.
Transactions that do not follow the script
Cards are sometimes accepted with no live approval at all, under floor limits, through offline authorization — and the merchant carries that risk alone. Hotels and fuel stations approve an estimate, then capture a different final figure. An order canceled before capture is a void and never reaches the cardholder's statement, while one canceled after capture is a refund that does.
Cost is the part of a card payment a merchant cannot influence from here. Interchange and scheme fees are fixed by the network, and only the acquirer's margin is open to negotiation.