Do you mean the guest checked out and didn't use the last night of the booking @Phyllis221 , and you want to give some sort of refund for that?
I would go to the booking, look at my host payout, divide by 2 and then use the "send/request money" button on the booking to refund the night's stay. Hopefully that means they'll be even happier to return and leave a great review next time (and this time).
However, if you don't want to give a cash refund and prefer to gift them a future night, all you can do is wait for them to request a trip at some point in future and then send them a special offer. When you promise them this discount, perhaps rather mention the amount - if you say "one night's stay", they may book in your very peak season next time? Or they may book five years from now when your rates are higher.
