Is it impermissible for a transaction conducted online to pay for goods priced in US dollars with British Pounds, where the currency conversion is automatically handled by the bank 1-3 days after the initial transaction based on the exchange rate on the settlement day?

There is no harm in purchasing a specific item available with the seller online, even if the payment is delayed in reaching them, as long as the item is not gold, silver, or currency, for which immediate on-the-spot exchange is a condition. However, if the item is not specific but rather described by its characteristics (dhimma), then the price must be paid at the time of the contract according to the majority of jurists. The Malikis, on the other hand, permit delaying it for two or three days.