Dear @Brad9
Of course its not your duty or responsiblity to refund their money. What this guests needs to do is contact Airbnb. Let the Airbnb staff explain to them what happens when they check out early.
What you can do is two things:
1. Give the guests the Toll Free number for the Airbnb customer service if they can't find it themselves IN THEIR BOOKING EMAIL....
and let Airbnb handle this. I learned the hard way when I tried to have a mature conversation with two young people about the same thing. Eventually Airbnb handled it and everything was settled quite well. I actually have the Airbnb customer service help line number in my guests room guidebook now.
2. OR......Negotiate an amount you are comfortable returning to them via the Airbnb resolution whether it be 50 % or 20%, up to you. But under no certain terms are you required to return anything. As I tell every host on this platform, your listing is your financial business. Handle it like a business and stand strong that if they had booked with a hotel, and decided to leave early, the hotel wouldn't be refunding them either. Dont' let anyone bully you, or make you feel bad, guilty or unsympathetic. Do what makes you feel comfortable.
AND......before you post another question about their possible negative reaction within their review, I can promise you that if they leave a review complaining about you not returning any monies for those 2 nights, contact Airbnb immediately as that is a violation of the Airbnb terms and they will remove the review immediately. (Do not tell them this, I am sharing this with you as a FYI) Good Luck. And let us know how it goes.
If you feel that me or another host have helped you, feel free to click on the "thumbs up" button at the end of any post. Thank you so much.
Aloha, Momi
Great way to contact Airbnb or via Twitter at AirbnbHelp / Facebook