While I am not 100% sure because I am neither a lawyer nor an accountant, If they add it on to the front end, they must tax it as income. Fees from Airbnb would need to be taken out of the whole and in some communities where they send taxes to the local organizations for "occupancy" on behalf of the host, this becomes a complication because a dog is not an "occupant" and they have to back that fee out. It's not that it can't be done, but it's not consistant across all countries, counties, towns, etc. It's an undo complication that benefits only an small number of hosts.
Additionally, for some hosts, an animal fee is variable. We charge the fee based on a variety of aspects including but not limited to age, breed, how long the animal is staying, does it sleep on the bed or not, will the hosts need to rent a crate while they are here with us, how many "pets", and if we need to provide food. By posting in our House Rules that we have a fee without annoucing it in advance, then people talk to us about their dogs first before booking and we have the option of saying no - we're sorry, but we can't host your iguana/tropical bird/snake/rabbit/rat or whatever they want to bring to our home. We are picky because, as animal owners, a dog on vacation can do all sorts of things that they would never do otherwise and vetting the owners is the only way to determine if they will be responsible. We recently noted in our rules, now that Emotional Support Animals are allowed free of charge with Airbnb, that we will not take any animal that does not do it's business outside - anything that deficates in a box, cage, tank, etc is not allowed.
Finally, it's very easy to collect this fee using the Resolution Center. Airbnb made using the Resolution Center much simplier to support asking for fees for "extras" so they they don't take out their fees from the bonus services some hosts provide. When we do an extra, mid-week cleaning and charge the guest, Airbnb doesn't take their cut of that. If we provide meals, no % to Airbnb. I personally don't want to start taxing the guests for animal fees any more than I want Airbnb taking a cut of the money I charge to host them. We don't even bother sending a price change, we just ask for the fee separately. It's nice and tidy and clean accounting. AND by using the Resolution Center, if the guest refuses to pay, Airbnb will act on my behalf to collect those funds. So someone who just "shows up" with a dog can be required to pay
Again, just adding my thoughts to this. BTW, in case you didn't notice, I seriously do not want this to be automated because I don't automatically want to take every dog, cat, ferret, or guinea pig just because someone can check the box in advance that they're bringing a pet and willing to pay to have it stay.
