@Marissa160
Airbnb's Terms of Service state:
"Except where expressly authorized, you may not allow any person to join a Host Service unless they are included as an additional guest during the booking process."
Whenever a guest breaks this rule, I always call Airbnb and ask Airbnb to inform the guest they no longer have a valid reservation and then, I always evict them.
I am pretty sure that the unauthorised guest wouldn't be covered by Airbnb's host liability insurance if something goes wrong and I am even more sure that if the unauthorised guest thought that they could sue you they would.
Different strokes for different folks but I would rather not put myself in a position where I lose my tourist licence and consequently the forthcoming guests lose their holiday because of the actions of a few undesirables.
I've never had any money deducted by Airbnb as a result of doing this.
I have, however, had at a couple of guests post on social media after the event proudly announcing that they'd been "kicked out of our Airbnb, not for the first time and probably not the last".
Says it all really.