If you have confirmed a booking and need to cancel, this can be done online through your NUCO account and booking here.  When you click 'cancel booking' this will generate the cancellation charge, this charge will come from what you have paid towards your booking already and is not an additional charge you will be required to pay.  

The cancellation charges for booking refs beginning 'NUCO-' are as follows:

Depending on your reason for cancelling your booking we would recommend looking at other options available to you. Firstly, a name change; this is where you can transfer your booking over to someone else, more details on Name Changes can be found here.  The other option would be looking at your travel insurance to see if the reason for your cancellation is covered by your travel insurance provider.