This can vary depending of the conditions of the local operators in the country where you are travelling, and will be written up clearly in your Trip Contract.
In general there is a non-refundable deposit to be paid. For our African safaris and our Kilimanjaro climbs we require a 20% deposit to be paid upon booking. Some or all of the deposit is non-refundable. All of our booking fee/initial deposits for our European journeys are also non-refundable, although the amount to be paid is a lot less that our safaris. This is because the camps and lodges we use in the African bush are often very small, sometimes with only 4 or 5 tents, and these ground operators rarely have enough time to fill space once a booking has cancelled. As a result they demand high deposits. The actual conditions depend on the accommodation booked, the country you will be travelling, and other details that will be included in your Trip Contract.