This is all slightly surprising. When you pay with Visa/Mastercard etc the money does not go straight to the operator's bank account. It goes to an intermediate financial organisation called a Merchant Card Provider, there are several, selected by the operator. They take your money (straight away) and hold it until released to the operator. There is a negotiated formula for how it is released dependent on the creditworthiness of the operator, but for holidays the bulk is held on to until advised that the service has actually been delivered. There's even interest paid to the operator, though not much nowadays. The operator can do refunds from here. This is how, if the operator goes under, the credit card organisations can refund the money - it never went through to the operator in the first place. MCPs are the ones who provide the terminals, which is how the same desktop terminal can serve all of Visa, Mastercard, etc.
MCPs moving the percentage they hold on to until service is complete is a common cause for airlines etc finally going under, when the percentage held gets moved from say 80 to 100 percent.
It appears in the operators' accounts as an Accounts Receivable asset.