Most credit card processors require a billing address in order to process a payment. However, Booking.com does not require the guests to enter the billing address when making a reservation. Most of the time, the end result is a declined transaction with an error code of: Required Field Not Supplied. You can see the error code in the reservation under the “Notes” tab.
If the guest did not provide a billing address through Booking.com, you should contact them for the missing information and then process the payment again. You may also create an entirely new payment.