@Quincy
Thanks for posting the link. I have had a look at the sections that you mentioned and it requires you to fill out a form. Perhaps I am being dim (I have always hated doing my accounts) but I can't make head nor tail of it. In one of the first sections, you have to tick a box to confirm which type of entity you are, but as far as I can see nothing there relates to a homeshare host who is paying tax on Airbnb income as a self-employed person.
I don't believe my payments have any US tax deducted, so it's probably not relevant to me anyway, but if they did, I would find this form extremely confusing to fill in. It also keeps referring to 'instructions' but there are no instructions attached.