In effect, it's a three way transaction, but each party can only access the information it needs to do its job. Taking credit card payments online for overnight processing is commercial insanity. In practice, realtime credit card transactions are pre-authorised to a set value provided the vendor checks card numbers against a supplied hot list. Transactions over the limit must be authorised. This doesn't guarantee you'll be paid but it eliminates the more incompetent criminals.
Authorisation is a two part process.
The authorising company runs the check with the card issuing bank then authorises or denies it immediately. Merchant Services Small or new companies and those with a small turnover may have to turn to a third party such as Earthport to handle credit and debit card sales, though banks are beginning to target ecommerce more aggressively. This enables its business customers to integrate online payments with their existing banking services. In fact, NatWest offers customers WorldPay software. This model is likely to be followed by other banks - though don't expect them to assume any of the risk.