Go to the Booking.com booking for which you need to mark the card as invalid. You will see a Booking.com tab:

Click the button "Mark credit card as invalid" if the details provided to you by Booking.com are not allowing you to take a payment.

Once you click the button it will send a request to Booking.com and they will request new card details from the guest and re-send them to you.
You have three attempts to obtain valid card details.