Each option has a refund ladder: how much a traveller gets back, depending on how early they cancel. Travellers see it before they pay and before they cancel.
Open the product and press Rates and dates. The Cancellation card sits below each option's prices.
Each line gives a refund and how many hours before the start it applies. After the last line, nothing is refunded.
In Options and tickets, Voucher and booking rules, ticking Non-refundable means nothing is refunded on cancellation, and checkout says so before payment.
Careful. Ticking Non-refundable and saving the page applies it to new bookings of that option. Leave it unticked if you offer refunds.
Tip. A booking keeps the terms it was sold under, even if you change them later.