Your SwapNights balance can go into a negative figure if you cancel a booking and the system charges a penalty of SwapNights in accordance with the cancellation policy and you do not have sufficient SwapNights to cover this penalty.
You can add SwapNights to your balance in the following ways:
1. Earn SwapNights: by having a Guest stay at your property
2. Confirm a new booking: If your SwapNights balance is negative at the time you Confirm a new booking as a Guest you will be charged for the number of SwapNights your account is in negative in addition to the Top Up SwapNights you are seeking to buy with this new booking.
SwapNights does not require members to restore their balance to positive - your account can sit in negative (and your membership remains fully active) until such time as you either earn SwapNights by having a Guest stay or by buying Top Up SwapNights in the process of making a new booking (in other words, you cannot Confirm a booking as a Guest without first restoring your balance by buying Top Up SwapNights to 'pay back' the negative SwapNights balance).