A card payment is approved in seconds and the money reaches the merchant days later. The two events are separate, and the gap is a feature of the system's design.
Authorisation and settlement are distinct steps
When a card is presented, a message travels to the issuing bank asking whether funds are available and whether the transaction looks legitimate.
An approval reserves the amount against the account and guarantees payment to the merchant, but no money has moved at that point.
Settlement happens later, when transactions are batched, netted between institutions and transferred through a clearing system on a defined schedule.
Netting reduces the volume of transfers
Rather than moving money for every transaction individually, banks calculate what they owe each other across all transactions in a period and transfer only the difference.
This reduces the number and value of interbank movements enormously, which lowers cost and reduces the liquidity each institution must hold to participate.
The consequence is that settlement runs on cycles rather than continuously, and payments made outside a cycle wait for the next one.
The delay is where risk is managed
The window between authorisation and settlement allows for reversals, disputes and fraud checks before funds have irreversibly changed hands.
Chargeback rights depend on this structure, since a card payment can be unwound in ways an immediate irrevocable transfer cannot.
Faster settlement therefore reduces the opportunity to intervene, which is one reason instant payment schemes have seen higher rates of authorised fraud.
Displayed balances are not settled balances
An app showing a payment immediately is reflecting the authorisation, and the pending amount reduces available funds without having left the account.
Pending transactions can expire, be amended or be released, which is why a hotel or fuel pre-authorisation can hold an amount different from the eventual charge.
The visible balance is therefore an operational figure maintained by the bank rather than a record of money that has actually moved.
Reconciling the two is what produces the occasional transaction that appears twice for a day, or vanishes and returns, without anything having gone wrong at either end.
Instant schemes change the trade-offs
Real-time payment systems settle continuously, so funds are transferred and final within seconds rather than at the end of a cycle.
This requires participants to hold liquidity available at all hours and removes the netting benefit, which raises the operational demands on each institution.
It also removes the reversal window, making these transfers effectively final, which shifts the burden of verification onto the payer before the payment is sent.