Every channel has different terms and conditions, some accept cancellations and some don't. When you connect in the 'How it works' section you will see their conditions. The majority of the channels don't accept cancellations and if you can't honour a booking, you will be asked to provide an alternative of equal or superior value to the guest. If you are not able to do this, some channels will charge you a cancellation fee, a relocation fee and/or you sometimes will also need to pay the difference between the rentals.
Please note: The agreement is between you and the channel directly. Rentals United can't cancel bookings or communicate on your behalf. Make sure your availability is always updated in Rentals United or in your PMS. If you use iCal links instead check carefully that you have entered them correctly and that the sync is working properly.