What happens if:
- I book a non-refundable room on booking.com;
- Credit card is invalid;
- The bank said the transaction failed;
- I cancel the booking.
What about the cancellation fee?
The card was declined before the booking was made. Therefore no contact existed, so there never was a booking to cancel. So there cannot be a cancellation fee.
This question has very little to do with travel and might be better posted in Money .