Can I tell if someone is trying to book on my portal with a stolen card?

Yes, in most cases you can spot a risky booking before it goes through, but no system can promise you that a card is genuine. Your portal can be set up to flag bookings that look unusual, such as several failed payment attempts in a row, a passenger name that does not match the cardholder, a departure that is only hours away, or the same person trying one card after another. Those bookings can be held for your staff to check instead of being confirmed straight away.

Most of the real checking happens at the payment step rather than in the booking screens. The card gateway you use runs its own fraud rules and asks the cardholder to confirm the payment with their bank, and that bank check is the strongest protection you have. How much detail you get back about why a payment was refused depends on the gateway and the plan you hold with them, so ask them directly what fraud tools are included before you rely on it.

It helps to be clear about where the money risk sits. If a booking is disputed later, the loss usually falls on whoever took the payment, and with flight tickets the danger is that the ticket is issued as soon as the payment clears, so the supplier has already been paid before the dispute arrives. Hotels booked on a pay at the hotel basis carry much less of this risk.

Ask your payment provider which fraud checks are switched on for your account, then decide which kinds of bookings you want your portal to hold for a manual look before they are confirmed.